The thing that worked best for me was modifying the stock thermostat to open about 10-12 F degrees cooler. If the climate's hot, won't do any good. Here in Denver, it's cool enough most of the time. Also just cave in and run premium fuel in summertime. $$
I changed my thermostat to the 160 degree from Hypertech along with the programming from the HPIII. Noticed that the trucks runs about 190 instead of 210 even on hot days.
After 3 trips to the dealer and 6 days of shop time, Champion Chevrolet has finally found a lead in the 5.3 knock problem.
After exhausting the Tech 2 analysis, the service manager called GM TAC which faxed directions for a more in depth check. In short, both knock sensors were found to to have faulty grounds to the engine block. One sensor tested at 15 k ohms @ idle, and 65 k ohms @ 2500 RPM. Factory spec is 100 k ohms. A loose ground would be consistent with the intermittent knocking. (More knock than not)
The dealer has ordered parts and will install them after I return from a restful Mexican holiday. Hopefully this problem is licked, and I'll get into the more interesting stuff like Bilsteins and Magnaflow. Plus a complaint to the GM rep for an extended warranty for the possible damage to my engine while driving Herr Knockwurst. More later.
P.S. Obyone, I've left the truck completely stock to this point. Don't want any more speed bumps than I already have with the dealer. Actually the dealer or I should say the service manager has been great. Up front and honest. R
is lack of acceleration, nothing a supercharger wouldn't cure. When discussing this with the service manager....he said it would be the quickest way to void the engine warranty along with the drivetrain. Perhaps creating more HP than the trans was designed for. Oh well, just have to wait another two years...
I'm interested in how this turns out with the knock sensors.
The thing that troubles me about your statement, is that just about always, an intermittent ground causes dc resistance to increase, not decrease. Like from 100K ohm to 1 meg ohm.
Since a knock sensor is basically, a microphone, the resistance will change with the level of sound from idle to 2500 rpm. How, or even if the PCM can extract the sound signature of spark knock...I don't know.
If it's out of spec as you describe, that doesn't sound like a faulty ground, but rather a faulty knock sensor. I doubt that. Good luck, and keep us posted?
Could this knocking harm the vehicle in future. I also have the knocking/pinging, or whatever else you want to call it, but it's not too bad. I wouldn't worry about it at all if I were sure it does not harm the motor.
Also, as I think I've stated before somewhere, I took my 4.8 to the service guy (different dealer obyone) to listen....he listened and then took me over to a 00 model in the shop and started the motor.....the 00 model made the same sound. We both laughed at the same time. He doesn't have a clue how to fix it. Apparently this is a hugh problem for GM.
Another dealer (my dealer) said it was Carbon Buildup (on truck with 26k miles). What the H#@$ is that? Maybe the Mobil 1 will clean it out..
GM has a special injector cleaner that they use to get rid of the carbon buildup. Another thing. You mentioned that the '00 made the same sound on start up.....check the '01...it doesn't.
Can I buy the "GM" cleaner anywhere else? The service advisor said he knew of no cure or treatment for the "carbon buildup" (if there is such a thing).
Also, what about this Techron (Chevron I believe) fuel treatment stuff....you ever tried it? Think it would hurt to try?
By-the-way, when I listened to the 00 model, the knock was the same tone, but not as loud as mine. However, it was same, etc.
I'm going to have to research that carbon buildup cleaner. I know that it does exist. That Techron stuff that Chevron sell for $9.99 can be found at Costco for 2/$5.99. It works on gummed up injectors, but not for the carbon buildup.
If you listen to a '01 model, there is no knock as GM has taken care of the problem.
I talked to a couple of other GM dealers today (different cities) and apparently this carbon buildup is for real. One dealer was very familiar with the knock and said he could fix it. Here's his solution: bring the truck in for over night visit. He takes the plugs out and pours substance down the holes. He then lets it sit overnight. The next date he puts plugs in and starts it up. He said that is smokes real bad for a miniute or two.
He said he has done 12 trucks this year and all have worked (no knock). He also said that the build-up usually starts between 20k and 30k miles. He does not know if the carbon buildup will return.
Well, fresh from a forgettable trek to Mexico and bearing gifts from Senor Montezuma, I've eagerly awaited the results of many days at the dealer dropping off and picking up my Z71.
The dealer replaced BOTH knock sensors, (the service bulletin called for replacing just the weaker one of the two), and the only difference is a little boost in power, but the knock problem is unchanged. The boost in power seems to verify the higher resistance measured in one of the sensors and justifies its replacement. But since the pinging remains virtually unchanged, this proves there is a separate issue apart from the faulty knock sensor. The tank is still half full of premium gas from the trip - there is something definitely wrong with this truck.
As long as the dealer will cooperate with me, I will continue to take it back until it either gets fixed or I've built enough of a case to have it replaced with a new one.
I believe the Silverado is essentially a good product, but this problem has been a major disappointement.
GM can fix this problem with a simple reflash of the PCM with the Tech II...if they wanted to. All that's needed is a slight retarding of the ignition timing. They just don't want to harm fuel mileage, which figures into their CAFE strategy.
As I have stated before, the thing that has worked best for me was to modify the thermostat to run about 10-12 degrees cooler. They have them running so friggin hot because it lowers emissions. The other thing I do is run the premium fuel in hot summer months. In the cool Colorado climate, this has solved it for me. But in a hotter climate, I might not be satisfied.
They run waay too clean and hot to have much carbon buildup in the combustion chamber. Mine was pinging by 7000 miles. A colder plug can also help. I simply don't buy the carbon buildup explanation. That kind of buildup infers unburned hydrocarbon byproducts. Fuel mileage is too good for this to be the case. They need to run them a little richer, and retard the timing a few degrees. They won't...so I'll review my entire ownership experience before automatically renewing with GM. But at this point in time, I'm still satisfied.
For some, the knocking problem is solved, or non-existent, in logarithmic proportion to dbV of the volume knob. You would not have to be hearing impaired to mask it. Mine in particular has never been a loud knock...just a light ping, usually on regular gas, hot day, a/c on. So I still wonder, and Dean would know from the Pacific Audio site and others, whether a little solvent is anything more than a placebo. If the Hypertech marketing people would offer detuning spark advance instead of just power tuning, I and a few other truck owners might consider it. It's irritating that spark timing is non-adjustable. Perhaps they will take my stroboscopic timing light it trade?
timing light that is...perhaps getting obsolete? LOL!!
After checking some notes that I had kept on the cleaner (not on computer) I had found it in a thick folder on Silverado fixes that I keep. Never had a part number on it and only have it referred to as "top engine cleaner". The cause of the carbon buildup was listed as "due to near skirtless pistons". Are the pistons of the female gender? The procedure calls for pouring the cleaner in while the engine is running thus killing the engine and letting it sit overnight. When starting the next day, it smokes similar to using the old style carburetor cleaner.
jed1894
After reading your post again, it seems that your knocking is on start up. That being the case, it may be caused by excessive rod and/or main bearing tolerances. The '00 and '99 do it on startup but since tightening the tolerances for '01, the '01 doesn't share the problem. The fix, if you can get a service department to do it is to change the main/rod bearings.... Hmmm...wonder what it would take to get a dealer to do that on a little knock...think it would be closer to an act of God. My $.02 and poor attempt at satire. Good luck!!
is basically transmission fluid, or Marvel oil. I posted on another topic about this. The description of pouring the chemical into the combustion chambers and letting it sit overnight is what we did back in the early '70s when the mfgs went with the really tall gear ratios and kept the engine rpms in the basement. Oh, yeah those babies would "load up" on carbon. We would run tranny fluid down the carb until the engine choked and died. Let it sit for a few hours and then fire it up. Smoke? Man, there were Greenpeace folks having fits. But when all the smoke cleared and the carbon broke loose from the tops of the cylinders, the engine would run better, idle smoother, and get better mileage with no pinging. Not only does the carbon dome (thats what it was called back then) raise the compression slightly, it can really screw up the airflow in and out of the cylinder. I add a quart of Marvel to a full tank of gas every 1-2K miles and have had no problems. Good luck,
I don't want that crap plugging up my expensive dual catalytic converters, or ending up in my crankcase oil.
I'll just wager your compression ratio hasn't been raised a bit by carbon buildup. What happens is you have a sharp edge in the chamber, machining flaw, casting flaw etc, that becomes a hot spot, glows red, causes preignition under conditions of excessive spark advance and lean mixtures. If they'd just let us back off the spark advance a bit...
I thought this stuff was designed for oil use--not gasoline. Meaning...put in oil tank not gas tank?
I think I'm wrong here because I remember putting the stuff in my airplane years ago. However, it was only cup or two to about 20-30 gallons of fuel. It was recommended by my airplane mechanic to enhance engine performance, etc. I don't know if it helped at all...... Furthermore, the airplane motor was a Lycoming (spelling?) and not as advance as today's engines.
jlflemmons: Do you use the Marvel Mystery Oil because of knock you had, or are you trying to avoid a knock? If you had a knock, did the oil fix the problem?
Another point.....why doesn't it knock all the time? It didn't do it at all today when I listened. Very frustrating when I'm trying to let the dealer listen to the noise.
your comments concerning the reflashing of the PCM to the local dealer service manager. I'm not sure how that process works, or even what the PCM is, (Pollution Control Module, Memory?) but my guess is it's a reprogramming of that unit to the original factory specs.
I agree that carbon build up anywhere in the engine could not be the culprit since I first noticed the light pinging at about 2000 miles.
At the dealer service manager's suggestion, I took the truck to a reputable Dyno/Tuning guy and he guaranteed (?!) he could he could solve the pinging by installing a 180 degree thermostat to cool the engine down a bit, and a Hypertech III to adjust the timing and fuel mixture. In short, the problem is a combination of temperature and fuel mixture, born from an auto industry under pressure to please the EPA. He did not mention whether a setting could be saved for either Regular or Premium. But in the end he really didn't want to take the $500 from me to fix a problem that belonged to GM in the first place, which of course is obvious.
Read what I said. "Not only does the carbon dome (thats what it was called back then) raise the compression slightly,it can really screw up the airflow in and out of the cylinder." ANYTHING added to the combustion chamber increases the compression ratio SLIGHTLY, as I said. And the ratio of one quart of Marvel to 26 gallons of fuel will not damage your precious dual catalytic converters. The reason the knock or ping comes and goes can be due to the buildup and breaking loose of carbon. It can also be caused by a knock sensor which is temperature sensitive. Many of the "oddities" in engine performance today are caused by variances in the sensors used as well as different additives used in the grades of gasoline. Here in Texas, premium grade fuels can give you fits during the summer months. If you have properly functioning knock sensors on an engine, and fuel/carbon buildup/whatever causes pre-detonation in the engine, the common symptom will be a loss of performance and fuel economy due to retarded timing. There is just so far that the timing can be retarded before the ECM will go no further. Otherwise, your engine could be retarded to the point it would not run at all if you got a really bad combo of fuel/old plugs/carbon/etc.
So, if you don't agree with my opinion, thats fine, but remember, this is a forum for discussion and opinion, and this is mine.
Jlflemmons, Sorry to be offensive, didn't mean to be...guess I was. Nevertheless, I respect your opinion, however my opinion mirrors Mr. Rogerz above. I simply don't believe there is much carbon buildup, and on that...we agree. I apologize for overemphasizing carbon buildup...you certainly stated it could be a "slight" amount, carbon dome etc. But...your opinion that the engine can be retarded to the point where it would not run at all if you had a bad combo....just doesn't fly with my experience over the years with adjustable timing distributors and stroboscopic timing lights. I've always been able to deal with ping, either inciting it with too much advancement, or quenching it by retarding, without ever approaching the point where the engine would not run. Those engines I'm sure, had more carbon buildup than the hot running, low emission, fuel efficient 5.3L. The culprit here is OBDII, where hundreds of parameters are under hardware control of the PCM (powertrain control module, just an automotive CPU). Parameters like spark timing are non adjustable, distributors have been replaced by optical crankshaft position sensors. You can't change anything without re-writing parameters to the flash (eprom) memory. Even the dealers have been removed from the equation. The best they can do is reflash factory updates. The factory has simply not allowed a sufficient tolerance to accommodate variances that occur during manufacturing. So most aren't affected I'm sure. The ones that are simply fall outside of allowable limits.
Sorry to be so long, but knock sensors vary dc resistance in proportion to sound waves. All resistors are somewhat temperature dependent. It's the guiding principle behind thermistors, a type of resistor used in your wifes hair dryer for protection from overheat. Resistance that increases in inverse proportion to heat. Temperature variability is expected, and allowed for, within limits which would be fairly accommodating to temperature change in an automotive application. Your opinion welcome, of course.
Mr. Rogerz, I simply have no comment regarding your statements because I am in total agreement with them.
I am from Texas, and never had problems, or even heard of problems from running premium fuel in summer, or any other time of year. If I am wrong, why is it offered?
The only difference between the fuel grades is the addition of octane. Octane in itself is not a fuel rating, and is commonly misunderstood. It is a chemical compound C8H18, an isomeric liquid paraffin hydrocarbon, added to make fuel burn more slowly. There is no benefit to having more than the engine can use. Problems occur when proper combustion demands more than the fuel supplies. The result is preignition.
Bringing this discussion around to full circle, the GM handbook states that oil and fuel additives are not recommended. It also states that a small amount of ping, as when accelerating up a hill is normal, but not a loud heavy knock. It also states that if you have a knock which requires changing to a higher fuel grade, you have an engine problem for the dealer. Markbuck, who owns the full GM service manual set, says he found a paragraph where it states the engine was designed for premium fuel. Obviously, there is some contradictory information coming from the factory. So if the best solution they allow the dealers is to let solvent soak in your cylinders overnight, dilute your oil etc., I'd rather do nothing. That's my opinion. On my truck, I modified the thermostat to help it run a little cooler. That's not a perfect fix either since it won't help in summer when the thermostat is open fully anyway. But in cooler months, it works great. That's the best I've been able, or willing to try. My opinion remains, GM is unwilling, or EPA won't let them, offer the simplest fix, a computer reflash retarding spark an extra few degrees, or enrichening the fuel delivery map. Everything else is a band aid.
I drive my '96 Z71 in California and have the problem with our emission gas clogging the fuel injectors. GM sent out a 10 year/ 100,000 mile warranty on the injectors for California residents. My personal mechanic read the TSB's and went and purchased the GM injector cleaner. It costs $16 a bottle. I went in to my local dealer and told the parts guy I know that GM doesn't make this stuff. What is it? He told me it is the Chevron Techroline injector cleaner. The bottles even have the same shape. He said when they run out of the GM stuff they run down to Costco, as posted earlier, and buy the two bigger bottles for six bucks.
Visited a different service manager today about the knock thing. He also told me it carbon build-up. He said he has pulled "heads" at different mileage and seen the carbon build-up.
He says that the cure could be done with a computer program by GM. So whoever mentioned that above was consistent with his comments.
He also said that using a fuel injector cleaner has helped in some cases, but not all.
He believes that GM is working on a TSB for the computer program to fix the problem (I've heard that before). He also recommended that I call the GM 800 number and get a case number in case the "fix" came out after my warranty expired. I'm going to do that tonight...I'll let you all know what happened.
I think you'd have problems if the injectors were changed, because the control loop gets closed, by the 02 sensors. The PCM would recognize the rich mixture from the 02 sensors, and decrease the "on" time of the injectors to compensate for the rich content seen at the exhaust. If it couldn't, you might get a trouble code. At least that's what I would expect, again unless someone has already tried with good results. Same for bigger fuel line. If you could recalibrate the 02 sensor, so the PCM thinks it's lean, you could get the same result without changing the injectors. Surprisingly, 02 sensors don't work all that differently than knock sensors. Like the KS, the 02 also changes dc resistance as carbon monoxide levels in the exhaust change. Again, I think the key device may be a thermistor. Carbon monoxide removes heat from a sensor at a different rate than air. A thermistor across a wheatstone bridge is how my old exhaust gas analyser works.
Cr500r, Your bike is a rocket. Too scary for me. But dirty injectors are not from octane. They just get dirty because fuel leaves varnish behind when it evaporates, and has a limited shelf life. Same gunk in your float bowl. It's another reason why propane, CNG are clean fuels.
quad, you are right about the varistor effect in the sensors. The problem occurs when the sensor has the wrong resistance for the temperature. A classic example was in a Fiero where the temp sensor that told the ECM the engine temp for rich mixture when cold was off by about 30%. Any time the engine temp went below 180F, the ECM would increase the pulse width for the TBI and dump extra fuel. Fortunately, I found the problem as the dealer could not figure it out. Only had the TBI catch fire once, and the air cleaner contained the damage until I got it put out. After that, my friends changed the spelling of the car to Fire-o.
The GM service manager here said the problem with the premium fuel isn't the octane, it is the other additives to improve emissions. He said the worst affected were the GM 4.3L CPI engine in the Astro/Safari and the 3.8L supercharged engine in the Bonneville SSI.
I won't even bore you with my two year battle on the '96 Vortec 5.7L ECM program. A "feature" in the software causes the throttle to not release at highway speeds for several seconds. The correction caused emissions to go up, so GM decided to leave it be. This is straight from a GM rep.
I'm curious as to which state you live in. According to Reed at the dyno shop, each state has its own emissions guidelines so I would guess GM would have to add each state"s guidelines into the equation in order to reflash the PCM, (reprogram the powertrain's CPU) to fix the knock problem.
I live in California, where the standards are the toughest, so it seems all manufactures have less tolerance for error to work with in their engineering and manufacturing, especially in this state.
The only place I've run across carbon build up as a possible cause for knock in new 5.3"s is in this topic. Older engines, 20k and up or there abouts, seem to be far more likely candidates for for this problem. The knocking in my 2000 Silverado is intermittent also. About 90% knocking 10% runs fine, which would indicate carbon would have to build up and blow out all by it's self to validate this theory. The weather, temperature or humidity or engine temperature have no effect on pinging.
A far more likely cause would be engine design trying to squeeze more mpg out of them and leaves tolerances so tight, manufacturing can't reasonably hold them. Again, Reed and Quad are in agreement with this. These engines run hotter and leaner than previous designs and any fix would include-
1 Lower engine temperature with a 180 degree thermostat. 2 Advance timing enough to burn fuel before it predetonates. 3 Increase or enrich fuel to air ratio for a cooler mixture to burn. 4 2 and 3 would require reprogramming of the PCM or a new aftermarket chip with a Hypertech III controller.
So, if engine manufacturing or defects resulting in a higher compression ratio or hot spots in 1 or 2 cylinders, which in turn causes the pinging, would altering the timing to correct the offending cylinders put undue stress on the ones that don't ping?
I have 6000 miles on this engine now and I first noticed pinging at about 2000 miles. I back off the gas when I hear the pinging but some times I either don't hear it or can't accommodate the problem because of driving conditions. What if any damage do I have to my engine at this point and what can I expect in the future assuming GM fixes this problem?
I am a printer and musician, and first time truck owner and not a mechanic. This is the first vehicle I've had the opportunity to modify and play with so to speak. I appreciate the input I've received on this forum and wish to thank Quad, Obyone and others your contributions to this topic. R
I live in Georgia now. I remember the tough emission regulations, etc. when I lived in northern California (1982-85). You guys protect everything out there (nothing wrong with that).
I agree with you on the knock problem. My knock is not constant either. It knocks about 50-60% of the time. As expected, it does not usually do it when I take it to the dealer.
Congratulations on your first truck. Maybe you'll be hooked and have trucks from now on. I've always owned trucks since age 16 (now 37). I've got my yankee wife (just kidding for you guys up north) hooked on them now. She would rather drive my 4x4 than her car.
I also agree with you on the help received from this site. The guys here are extremely helpful and full of information. Most of the GM topics are pleasant and easy-going. Every now and then some smart a@# will come and aggravate everyone.
Have any of you called GM customer assist? Did you know that it is not a GM employee that you are talking to? HUH? Yep. When talking to a "rep" on the phone it is not a person employed by GM, it is their call answering service...check it out:
I finally called the 800 number in my owners manual and got a case number. The Rep immediately accessed the survey I returned from my first trip to the dealer attempting to fix the knock and asked if I had received a call from them. I hadn't. She apologized. In fact, she was really nice. Perhaps they're cleaning house over there.
Checked out the GM sucks site. I bookmarked it, and the flamer thread looked like a script from Jerry Springer. Thanks, R
Springer has developed quite a reputation. Maybe someone should turn him on to GM. Nah, GM's laundry isn't dirty enough for him.
About the cleaning house, it seems to be self perpetuating from what I understand...
I do give GM cust assist credit for one thing, when I called they had no hesitation to set up a conference call with the service advisor or service manager at my dealership. Of course, it made no difference as nothing was gained by it.
In talking to the dealer service manager about another possible cause of my ping problem, he illustrated with this story:
A Corvette owner came in 3 times with damaged catalytic converters and had them replaced each time under warranty. The service manager thought there must be another cause for this other than defective cats. Upon inspection of the K&N oil bath filter the owner had installed aftermarket, they found the filter was way over saturated with oil, thus causing over $4500 in damage total. Not the same as adding a quart of Mystery oil per 26 gallons, but it's a bit of an eye opener.
Tomorrow morning I'll ride with the service manager and the mechanic with the engine hooked up to a device that supposed to pick up intermittent problems and show off this darned ping. Not the Tech 2. I'm anxious for a solution to this aggravation.
Also, can any one tell me what damage is done to the engine after prolonged pinging? I've known about burnt valves, rings and cylinder walls. aren't crank bearings affected too,
I had a 360 in my old 77 Dodge power wagon that had a leaking intake(took like 6 sets of gaskets to stop)and it made it ping really bad. How DC can STILL have problems with this after the nearly 35 years making the LA engine family is mind boggling to me, new Rams have the same leak, and they ping from it too...I test drove one with 15 miles on it that pinged like my truck did in 77.. One of the real bad signs is little black balls on the spark plugs. This is aluminum that is supposed to be part of your pistons! Pinging itself doesn't cause burnt valves, it's being really (excessively) lean that does it. I've seen exhaust valves that were burnt at 12000 miles that were call chipped up or sunk into the head. A friend had an Olds Cutlass that pinged all the time, nothing seemed to stop it. The best gas available, octane booster, a lower temp stat, colder plugs, slowing down the advance, and backing down the initial timing did very little. When it had about 60K on it, it made a very odd noise when it started up one morning. Stupidly, he drove it to the dealer. It didn't make it, it spun a bearing a mile or so from home. The mains and cam bearings were bad, 2 pistons showed signs of old meltdowns, and one was cracked along a ring land. Surprisingly, amazingly, GM put a new motor in it for free! I guess because it pinged almost from the day he bought it. It's still running around today, looks like hell, but runs fine. This motor never has pinged. If your truck pings like some of them do, all you have to do is open a window while driving slowly up hill. I heard one a few days ago (2000 Silverado) that really clacked bad. It was an extended cab 2wd. If the service manager and mechanic can't hear it( your ping), and you can, see if there is a younger woman (better hearing than men usually) working there that can go to verify the ping. I complained about the ping in my Dodge at about the 6k mark, and two mechanics couldn't hear it. But the receptionist could! She came out and asked one of the mechanics to give her a ride to the hospital, her husband had broken his arm in a fall. I volunteered to give her and the "deaf" mechanic a ride, and she couldn't believe that they couldn't hear it before. Back at the dealer, the mechanic got a piece of rubber hose, stuck it under the hood of my truck near the carb. We went around the block with him having the hose stuck in his ear, THEN, he could hear it!!! My present(2000 Sierra) truck does it very slightly at around 40 with my foot barely touching the gas pedal. I can barely hear it. I either have to have the windows open, or have everything turned off inside to hear it. It seems to have gotten better since I drive it really hard once a week. I leave it in 2nd, and get some revs on the motor. I'm convinced at least part of it is the motors too lean at idle/near idle, my exhaust pipe is almost new looking INSIDE after 6000 miles.
Damage, if any is going to be to the top end, not the bottom end, or bearings. If the electrodes on your spark plugs are in good shape, I wouldn't expect there to be much problem elsewhere. If there was any melting...different story. Severe ping or knock puts holes in the piston top and melts electrodes. This can be checked with a mirror and light, with spark plug removed. The kind of damage I would expect from the prolonged mild pinging might not show up for 150-200K miles.
The Tech II scanner can display a variable for "Knock Retard." My guess is that your knock sensors are working, but the allowable limit for retarding the spark timing is reached before the ping goes away. Knock retard is enabled when the knock sensor hears the ping. So it really isn't necessary for it to be audible to the service advisor if it shows up in the data.
I stopped using K&N oiled reusable filters after I got grimy, oily deposits inside my intake runners on a car I owned previously. They flow more air, but trap less dirt. Good for performance, bad for longevity.
If the factory would simply allow a larger limit for the spark timing to be retarded, they could make the problem go away in 5 minutes.
The problem with older vehicles, like that 77 model was you had another variable to consider, dwell, i.e., the points gap.
Ignition points haven't been used for a long time now, ever since solid state CDI ingnitions, and hall effect sensor triggers.
Even on an older car, if you couldn't tune out the ping with adjustments to the ignition timing, then you had other serious problems, stretched timing chains, improper fuel mixture, worn distributors etc.
I can sure see how over oiling would cause problems in the Vette, or any of the newer cars. Think about the airflow sensors in the intake and imagine what the oil would do to the readings. Converter failure can be caused by an over rich condition which will foul the converter, or even an over lean condition which can elevate the exhaust temp sky high.
Or it still could be, but it could be an exhaust problem. This is the conclusion that the Service Manager and mechanic came up with after test driving with the Tech 2 hooked up. The Knock Retard was functioning, up to 25 or 28 degrees from what I could see while driving proving the knock sensors were working. Driving around Manhattan Beach at morning rush hour to try and duplicate the ping was a bit difficult. I can best duplicate the noise on the freeway cruising around 50 - 65 miles per hour and lightly accelerate and it pings like crazy. Anyway,we stopped and revved the engine in drive while braked and stationary, and the noise was there although muffled. At this point the mechanic said an exhaust problem could be the culprit.
Cutting to the chase here, I'll leave it again at the dealers on Monday so they can soak the engine in Techroline. Apparently GM TAC (Technical Assistance Center) advised him to use this on another 2000 Silverado 5.3 like mine with 6000 miles on it to remove, you guessed it, carbon deposits. They told him that during the break-in period of 5000 to 10000 miles, unburnt gas can slip through the rings and valves and leave deposits. He thought it was BS (Bird Snot), but since the customer was serviced he hasn't heard from him. Go figure. Apologies to jlflemmons. This procedure should either eliminate the ping, or eliminate pre-detonation as the cause. Maybe, we'll see.
The next step after that they'll look into the Exhaust Gas Recirculator to see if it is opening and closing properly. The mechanic explained that the exhaust system is designed to operate with back pressure, and one of the components in the system could be malfunctioning and rattling.
Quad, thanks for the info. Hopefully the problem is not pre-detonation after all. I'll ask about maximum knock retard.
nrd525, that story made me LOL & walk away. I just wonder what type of hose he was using. Factory or aftermarket?
Oby, I think he did say eva 2, bit all I saw was the Tech 2 this time out. The mechanic seemed proficient enough.
This is how I know....>>>I can best duplicate the noise on the freeway cruising around 50 - 65 miles per hour and lightly accelerate and it pings like crazy.<<< ************************************ I'm sure it's not the EGR. It turns on a code if it has a problem. As for carbon buildup...even a brand new engine turns the top of a piston black before you drive it off the lot.
Regretably, I'm quite positive if your maximum knock retard were allowed to go to 35 degrees, there wouldn't be any ping no matter how much carbon buildup was in there. At that setting, you would have no adverse affect on fuel mileage, and would be splitting hairs on the emissions increase. I have too much experience on this to discount. The 35 degrees of retard would be from the maximum advanced setting, so this would still work out to an actual firing point about 3-5 degrees before top dead center. It's a pity they don't allow us to do what's right. You own it, afterall.
dealer for warranty work, had to remove HPIII programming as recommended by Hypertech. When I first programmed the changes I didn't notice much and thought Hypertech was a joke. Yesterday, when removing the programming, notice that the rado, with stock programming, actually ran like crap. I guess the saying is true, you don't miss it if you never had it.
Hmmm, I guess you weren't old enough to remember, but all GM and Chrysler vehicles had gone to electronic ignition by 75(GM) and 74 (Chry). I don't know if Ford was by then, but it wasn't long after that if they weren't. Dwell was in the past, along with those damn points . It was the modules cauing problems after that. I don't know how many of those black Mopar igniton controllers I went through when I lived out west. I was hitting the junkyards pretty heavy looking for them, and always had at least 2 of them available. One to carry around with me, so I wouldn't get stuck someplace, and another to replace that one, so I wouldn't be stuck before I could get to the junkyard to grab a couple more. And no, the new ones I bought from the dealer weren't any better at taking the heat than the junkyard ones were, and they cost ten times as much. I finally got one that solved the problem, and MSD6C box that replaced the Mopar module. Then I had to get new plug wires...
Since i've owned nothing but Chevrolet trucks I had to have the 99 chevy.My chevy was specially made.It came with woodgrain everywhere,overhead console,16 inch rims,paint that changes colors,running boards,billet grill,and a performance exhaust. Since the time of purchase i've installed two 4 inch tv's on the sun visors an Airaid air flow system that gives me 25 extra horses,and a hyperchip that lets me control the power of my motor.which of coarse reaches 325 horses and top speeds of 178 miles per hour.In my neighborhood i'm the only 15 year old that drives his parents truck to school and to work.
Comments
Bonnie Rick
Conferences Manager, Edmunds.com Town Hall
After exhausting the Tech 2 analysis, the service manager called GM TAC which faxed directions for a more in depth check. In short, both knock sensors were found to to have faulty grounds to the engine block. One sensor tested at 15 k ohms @ idle, and 65 k ohms @ 2500 RPM. Factory spec is 100 k ohms. A loose ground would be consistent with the intermittent knocking. (More knock than not)
The dealer has ordered parts and will install them after I return from a restful Mexican holiday. Hopefully this problem is licked, and I'll get into the more interesting stuff like Bilsteins and Magnaflow. Plus a complaint to the GM rep for an extended warranty for the possible damage to my engine while driving Herr Knockwurst. More later.
P.S. Obyone, I've left the truck completely stock to this point. Don't want any more speed bumps than I already have with the dealer. Actually the dealer or I should say the service manager has been great. Up front and honest. R
The thing that troubles me about your statement, is that just about always, an intermittent ground causes dc resistance to increase, not decrease. Like from 100K ohm to 1 meg ohm.
Since a knock sensor is basically, a microphone, the resistance will change with the level of sound from idle to 2500 rpm. How, or even if the PCM can extract the sound signature of spark knock...I don't know.
If it's out of spec as you describe, that doesn't sound like a faulty ground, but rather a faulty knock sensor. I doubt that. Good luck, and keep us posted?
Also, as I think I've stated before somewhere, I took my 4.8 to the service guy (different dealer obyone) to listen....he listened and then took me over to a 00 model in the shop and started the motor.....the 00 model made the same sound. We both laughed at the same time. He doesn't have a clue how to fix it. Apparently this is a hugh problem for GM.
Another dealer (my dealer) said it was Carbon Buildup (on truck with 26k miles). What the H#@$ is that? Maybe the Mobil 1 will clean it out..
John
Also, what about this Techron (Chevron I believe) fuel treatment stuff....you ever tried it? Think it would hurt to try?
By-the-way, when I listened to the 00 model, the knock was the same tone, but not as loud as mine. However, it was same, etc.
John
If you listen to a '01 model, there is no knock as GM has taken care of the problem.
He said he has done 12 trucks this year and all have worked (no knock). He also said that the build-up usually starts between 20k and 30k miles. He does not know if the carbon buildup will return.
All covered under warranty.
John
Thanks
John
The dealer replaced BOTH knock sensors, (the service bulletin called for replacing just the weaker one of the two), and the only difference is a little boost in power, but the knock problem is unchanged. The boost in power seems to verify the higher resistance measured in one of the sensors and justifies its replacement. But since the pinging remains virtually unchanged, this proves there is a separate issue apart from the faulty knock sensor. The tank is still half full of premium gas from the trip - there is something definitely wrong with this truck.
As long as the dealer will cooperate with me, I will continue to take it back until it either gets fixed or I've built enough of a case to have it replaced with a new one.
I believe the Silverado is essentially a good product, but this problem has been a major disappointement.
More later, R
As I have stated before, the thing that has worked best for me was to modify the thermostat to run about 10-12 degrees cooler. They have them running so friggin hot because it lowers emissions. The other thing I do is run the premium fuel in hot summer months. In the cool Colorado climate, this has solved it for me. But in a hotter climate, I might not be satisfied.
They run waay too clean and hot to have much carbon buildup in the combustion chamber. Mine was pinging by 7000 miles. A colder plug can also help. I simply don't buy the carbon buildup explanation. That kind of buildup infers unburned hydrocarbon byproducts. Fuel mileage is too good for this to be the case. They need to run them a little richer, and retard the timing a few degrees. They won't...so I'll review my entire ownership experience before automatically renewing with GM. But at this point in time, I'm still satisfied.
After checking some notes that I had kept on the cleaner (not on computer) I had found it in a thick folder on Silverado fixes that I keep. Never had a part number on it and only have it referred to as "top engine cleaner". The cause of the carbon buildup was listed as "due to near skirtless pistons". Are the pistons of the female gender? The procedure calls for pouring the cleaner in while the engine is running thus killing the engine and letting it sit overnight. When starting the next day, it smokes similar to using the old style carburetor cleaner.
jed1894
After reading your post again, it seems that your knocking is on start up. That being the case, it may be caused by excessive rod and/or main bearing tolerances. The '00 and '99 do it on startup but since tightening the tolerances for '01, the '01 doesn't share the problem. The fix, if you can get a service department to do it is to change the main/rod bearings.... Hmmm...wonder what it would take to get a dealer to do that on a little knock...think it would be closer to an act of God. My $.02 and poor attempt at satire. Good luck!!
I add a quart of Marvel to a full tank of gas every 1-2K miles and have had no problems. Good luck,
Jim
I don't want that crap plugging up my expensive dual catalytic converters, or ending up in my crankcase oil.
I'll just wager your compression ratio hasn't been raised a bit by carbon buildup. What happens is you have a sharp edge in the chamber, machining flaw, casting flaw etc, that becomes a hot spot, glows red, causes preignition under conditions of excessive spark advance and lean mixtures. If they'd just let us back off the spark advance a bit...
I think I'm wrong here because I remember putting the stuff in my airplane years ago. However, it was only cup or two to about 20-30 gallons of fuel. It was recommended by my airplane mechanic to enhance engine performance, etc. I don't know if it helped at all...... Furthermore, the airplane motor was a Lycoming (spelling?) and not as advance as today's engines.
jlflemmons:
Do you use the Marvel Mystery Oil because of knock you had, or are you trying to avoid a knock? If you had a knock, did the oil fix the problem?
Another point.....why doesn't it knock all the time? It didn't do it at all today when I listened. Very frustrating when I'm trying to let the dealer listen to the noise.
JOhn
I agree that carbon build up anywhere in the engine could not be the culprit since I first noticed the light pinging at about 2000 miles.
At the dealer service manager's suggestion, I took the truck to a reputable Dyno/Tuning guy and he guaranteed (?!) he could he could solve the pinging by installing a 180 degree thermostat to cool the engine down a bit, and a Hypertech III to adjust the timing and fuel mixture. In short, the problem is a combination of temperature and fuel mixture, born from an auto industry under pressure to please the EPA. He did not mention whether a setting could be saved for either Regular or Premium. But in the end he really didn't want to take the $500 from me to fix a problem that belonged to GM in the first place, which of course is obvious.
To be continued, R
If you have properly functioning knock sensors on an engine, and fuel/carbon buildup/whatever causes pre-detonation in the engine, the common symptom will be a loss of performance and fuel economy due to retarded timing. There is just so far that the timing can be retarded before the ECM will go no further. Otherwise, your engine could be retarded to the point it would not run at all if you got a really bad combo of fuel/old plugs/carbon/etc.
So, if you don't agree with my opinion, thats fine, but remember, this is a forum for discussion and opinion, and this is mine.
Sorry to be offensive, didn't mean to be...guess I was. Nevertheless, I respect your opinion, however my opinion mirrors Mr. Rogerz above. I simply don't believe there is much carbon buildup, and on that...we agree. I apologize for overemphasizing carbon buildup...you certainly stated it could be a "slight" amount, carbon dome etc. But...your opinion that the engine can be retarded to the point where it would not run at all if you had a bad combo....just doesn't fly with my experience over the years with adjustable timing distributors and stroboscopic timing lights. I've always been able to deal with ping, either inciting it with too much advancement, or quenching it by retarding, without ever approaching the point where the engine would not run. Those engines I'm sure, had more carbon buildup than the hot running, low emission, fuel efficient 5.3L. The culprit here is OBDII, where hundreds of parameters are under hardware control of the PCM (powertrain control module, just an automotive CPU). Parameters like spark timing are non adjustable, distributors have been replaced by optical crankshaft position sensors. You can't change anything without re-writing parameters to the flash (eprom) memory. Even the dealers have been removed from the equation. The best they can do is reflash factory updates. The factory has simply not allowed a sufficient tolerance to accommodate variances that occur during manufacturing. So most aren't affected I'm sure. The ones that are simply fall outside of allowable limits.
Sorry to be so long, but knock sensors vary dc resistance in proportion to sound waves. All resistors are somewhat temperature dependent. It's the guiding principle behind thermistors, a type of resistor used in your wifes hair dryer for protection from overheat. Resistance that increases in inverse proportion to heat. Temperature variability is expected, and allowed for, within limits which would be fairly accommodating to temperature change in an automotive application. Your opinion welcome, of course.
Mr. Rogerz,
I simply have no comment regarding your statements because I am in total agreement with them.
The only difference between the fuel grades is the addition of octane. Octane in itself is not a fuel rating, and is commonly misunderstood. It is a chemical compound C8H18, an isomeric liquid paraffin hydrocarbon, added to make fuel burn more slowly. There is no benefit to having more than the engine can use. Problems occur when proper combustion demands more than the fuel supplies. The result is preignition.
Bringing this discussion around to full circle, the GM handbook states that oil and fuel additives are not recommended. It also states that a small amount of ping, as when accelerating up a hill is normal, but not a loud heavy knock. It also states that if you have a knock which requires changing to a higher fuel grade, you have an engine problem for the dealer. Markbuck, who owns the full GM service manual set, says he found a paragraph where it states the engine was designed for premium fuel. Obviously, there is some contradictory information coming from the factory. So if the best solution they allow the dealers is to let solvent soak in your cylinders overnight, dilute your oil etc., I'd rather do nothing. That's my opinion. On my truck, I modified the thermostat to help it run a little cooler. That's not a perfect fix either since it won't help in summer when the thermostat is open fully anyway. But in cooler months, it works great. That's the best I've been able, or willing to try. My opinion remains, GM is unwilling, or EPA won't let them, offer the simplest fix, a computer reflash retarding spark an extra few degrees, or enrichening the fuel delivery map. Everything else is a band aid.
He says that the cure could be done with a computer program by GM. So whoever mentioned that above was consistent with his comments.
He also said that using a fuel injector cleaner has helped in some cases, but not all.
He believes that GM is working on a TSB for the computer program to fix the problem (I've heard that before). He also recommended that I call the GM 800 number and get a case number in case the "fix" came out after my warranty expired. I'm going to do that tonight...I'll let you all know what happened.
Just thought I pass this along.....
John
Cr500r,
Your bike is a rocket. Too scary for me. But dirty injectors are not from octane. They just get dirty because fuel leaves varnish behind when it evaporates, and has a limited shelf life. Same gunk in your float bowl. It's another reason why propane, CNG are clean fuels.
The GM service manager here said the problem with the premium fuel isn't the octane, it is the other additives to improve emissions. He said the worst affected were the GM 4.3L CPI engine in the Astro/Safari and the 3.8L supercharged engine in the Bonneville SSI.
I won't even bore you with my two year battle on the '96 Vortec 5.7L ECM program. A "feature" in the software causes the throttle to not release at highway speeds for several seconds. The correction caused emissions to go up, so GM decided to leave it be. This is straight from a GM rep.
John
I live in California, where the standards are the toughest, so it seems all manufactures have less tolerance for error to work with in their engineering and manufacturing, especially in this state.
The only place I've run across carbon build up as a possible cause for knock in new 5.3"s is in this topic. Older engines, 20k and up or there abouts, seem to be far more likely candidates for for this problem. The knocking in my 2000 Silverado is intermittent also. About 90% knocking 10% runs fine, which would indicate carbon would have to build up and blow out all by it's self to validate this theory. The weather, temperature or humidity or engine temperature have no effect on pinging.
A far more likely cause would be engine design trying to squeeze more mpg out of them and leaves tolerances so tight, manufacturing can't reasonably hold them. Again, Reed and Quad are in agreement with this. These engines run hotter and leaner than previous designs and any fix would include-
1 Lower engine temperature with a 180 degree thermostat.
2 Advance timing enough to burn fuel before it predetonates.
3 Increase or enrich fuel to air ratio for a cooler mixture to burn.
4 2 and 3 would require reprogramming of the PCM or a new aftermarket chip with a Hypertech III controller.
So, if engine manufacturing or defects resulting in a higher compression ratio or hot spots in 1 or 2 cylinders, which in turn causes the pinging, would altering the timing to correct the offending cylinders put undue stress on the ones that don't ping?
I have 6000 miles on this engine now and I first noticed pinging at about 2000 miles. I back off the gas when I hear the pinging but some times I either don't hear it or can't accommodate the problem because of driving conditions. What if any damage do I have to my engine at this point and what can I expect in the future assuming GM fixes this problem?
I am a printer and musician, and first time truck owner and not a mechanic. This is the first vehicle I've had the opportunity to modify and play with so to speak. I appreciate the input I've received on this forum and wish to thank Quad, Obyone and others your contributions to this topic. R
I agree with you on the knock problem. My knock is not constant either. It knocks about 50-60% of the time. As expected, it does not usually do it when I take it to the dealer.
Congratulations on your first truck. Maybe you'll be hooked and have trucks from now on. I've always owned trucks since age 16 (now 37). I've got my yankee wife (just kidding for you guys up north) hooked on them now. She would rather drive my 4x4 than her car.
I also agree with you on the help received from this site. The guys here are extremely helpful and full of information. Most of the GM topics are pleasant and easy-going. Every now and then some smart a@# will come and aggravate everyone.
Good luck
John
Have any of you called GM customer assist? Did you
know that it is not a GM employee that you are
talking to? HUH? Yep. When talking to a "rep" on
the phone it is not a person employed by GM, it is
their call answering service...check it out:
http://www.sitel.com/html/press/c_glo_990216b.html
Ever wondered why you had rude people
answering...well now you know.
You can check out this site as well:
http://complaints.gmacsucks.com/commun_v3/scripts/thread.pl
check out the thread entitled: 1-800 we don't give
a s**t
John
Checked out the GM sucks site. I bookmarked it, and the flamer thread looked like a script from Jerry Springer. Thanks, R
About the cleaning house, it seems to be self perpetuating from what I understand...
I do give GM cust assist credit for one thing, when I called they had no hesitation to set up a conference call with the service advisor or service manager at my dealership. Of course, it made no difference as nothing was gained by it.
A Corvette owner came in 3 times with damaged catalytic converters and had them replaced each time under warranty. The service manager thought there must be another cause for this other than defective cats. Upon inspection of the K&N oil bath filter the owner had installed aftermarket, they found the filter was way over saturated with oil, thus causing over $4500 in damage total. Not the same as adding a quart of Mystery oil per 26 gallons, but it's a bit of an eye opener.
Tomorrow morning I'll ride with the service manager and the mechanic with the engine hooked up to a device that supposed to pick up intermittent problems and show off this darned ping. Not the Tech 2. I'm anxious for a solution to this aggravation.
Also, can any one tell me what damage is done to the engine after prolonged pinging? I've known about burnt valves, rings and cylinder walls. aren't crank bearings affected too,
Film at 11. Roger
One of the real bad signs is little black balls on the spark plugs. This is aluminum that is supposed to be part of your pistons! Pinging itself doesn't cause burnt valves, it's being really (excessively) lean that does it. I've seen exhaust valves that were burnt at 12000 miles that were call chipped up or sunk into the head.
A friend had an Olds Cutlass that pinged all the time, nothing seemed to stop it. The best gas available, octane booster, a lower temp stat, colder plugs, slowing down the advance, and backing down the initial timing did very little. When it had about 60K on it, it made a very odd noise when it started up one morning. Stupidly, he drove it to the dealer. It didn't make it, it spun a bearing a mile or so from home. The mains and cam bearings were bad, 2 pistons showed signs of old meltdowns, and one was cracked along a ring land. Surprisingly, amazingly, GM put a new motor in it for free! I guess because it pinged almost from the day he bought it. It's still running around today, looks like hell, but runs fine. This motor never has pinged.
If your truck pings like some of them do, all you have to do is open a window while driving slowly up hill. I heard one a few days ago (2000 Silverado) that really clacked bad. It was an extended cab 2wd.
If the service manager and mechanic can't hear it( your ping), and you can, see if there is a younger woman (better hearing than men usually) working there that can go to verify the ping. I complained about the ping in my Dodge at about the 6k mark, and two mechanics couldn't hear it. But the receptionist could! She came out and asked one of the mechanics to give her a ride to the hospital, her husband had broken his arm in a fall. I volunteered to give her and the "deaf" mechanic a ride, and she couldn't believe that they couldn't hear it before. Back at the dealer, the mechanic got a piece of rubber hose, stuck it under the hood of my truck near the carb. We went around the block with him having the hose stuck in his ear, THEN, he could hear it!!!
My present(2000 Sierra) truck does it very slightly at around 40 with my foot barely touching the gas pedal. I can barely hear it. I either have to have the windows open, or have everything turned off inside to hear it. It seems to have gotten better since I drive it really hard once a week. I leave it in 2nd, and get some revs on the motor. I'm convinced at least part of it is the motors too lean at idle/near idle, my exhaust pipe is almost new looking INSIDE after 6000 miles.
Barry
The Tech II scanner can display a variable for "Knock Retard." My guess is that your knock sensors are working, but the allowable limit for retarding the spark timing is reached before the ping goes away. Knock retard is enabled when the knock sensor hears the ping. So it really isn't necessary for it to be audible to the service advisor if it shows up in the data.
I stopped using K&N oiled reusable filters after I got grimy, oily deposits inside my intake runners on a car I owned previously. They flow more air, but trap less dirt. Good for performance, bad for longevity.
Tuned in for news at 11 pm. Regards.
The problem with older vehicles, like that 77 model was you had another variable to consider, dwell, i.e., the points gap.
Ignition points haven't been used for a long time now, ever since solid state CDI ingnitions, and hall effect sensor triggers.
Even on an older car, if you couldn't tune out the ping with adjustments to the ignition timing, then you had other serious problems, stretched timing chains, improper fuel mixture, worn distributors etc.
Jim
Cutting to the chase here, I'll leave it again at the dealers on Monday so they can soak the engine in Techroline. Apparently GM TAC (Technical Assistance Center) advised him to use this on another 2000 Silverado 5.3 like mine with 6000 miles on it to remove, you guessed it, carbon deposits. They told him that during the break-in period of 5000 to 10000 miles, unburnt gas can slip through the rings and valves and leave deposits. He thought it was BS (Bird Snot), but since the customer was serviced he hasn't heard from him. Go figure. Apologies to jlflemmons. This procedure should either eliminate the ping, or eliminate pre-detonation as the cause. Maybe, we'll see.
The next step after that they'll look into the Exhaust Gas Recirculator to see if it is opening and closing properly. The mechanic explained that the exhaust system is designed to operate with back pressure, and one of the components in the system could be malfunctioning and rattling.
Quad, thanks for the info. Hopefully the problem is not pre-detonation after all. I'll ask about maximum knock retard.
nrd525, that story made me LOL & walk away. I just wonder what type of hose he was using. Factory or aftermarket?
Oby, I think he did say eva 2, bit all I saw was the Tech 2 this time out. The mechanic seemed proficient enough.
Everybody, thanks again for all you help, R
************************************
I'm sure it's not the EGR. It turns on a code if it has a problem. As for carbon buildup...even a brand new engine turns the top of a piston black before you drive it off the lot.
Regretably, I'm quite positive if your maximum knock retard were allowed to go to 35 degrees, there wouldn't be any ping no matter how much carbon buildup was in there. At that setting, you would have no adverse affect on fuel mileage, and would be splitting hairs on the emissions increase. I have too much experience on this to discount. The 35 degrees of retard would be from the maximum advanced setting, so this would still work out to an actual firing point about 3-5 degrees before top dead center. It's a pity they don't allow us to do what's right. You own it, afterall.
And no, the new ones I bought from the dealer weren't any better at taking the heat than the junkyard ones were, and they cost ten times as much. I finally got one that solved the problem, and MSD6C box that replaced the Mopar module. Then I had to get new plug wires...
Ryan