Did you recently take on (or consider) a loan of 84 months or longer on a car purchase?
A reporter would like to speak with you about your experience; please reach out to PR@Edmunds.com by 7/22 for details.
A reporter would like to speak with you about your experience; please reach out to PR@Edmunds.com by 7/22 for details.
Options
1999 Chevy Silverado 5.3 knock @ RPM
This discussion has been closed.
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