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Comments
I have a 1999 Tahoe with 134K. I went on a 500mi round trip and returned home. The next day I tried to start the car, motor turned over very well, strong battery and voltage, but it would not fire and has not since.
First- I had already replaced the fuel pump (and filter) with an AC Delco 3 months prior. The pump still sounded very strong, I checked the shraeder valve at the fuel rail and there appears to be plenty of fuel (50psi+).
Next step- I checked the spark figuring something wore out. Turns out I have enough spark to arc weld with.
Next- Poured gas in the throat (a fairly large amount) and the car sputtered to life for approx 2-3 seconds.
Diagnosis- We figured only when we absolutely flood the injectors with fuel will the car even attempt to fire, could this mean my injectors arent openning at the correct time? If so, we thought possibly replacing the ignition control module might fix this, does that control the firing of the injectors? I know there is a test with a voltage meter to check this, but I do not know the specific test.
Please help, any and all information would be greatly appreciated- I hate to just throw parts at a problem if someone else has a better idea!
Replaced the CKP- Crankshaft Positioning Sensor and the Tahoe started up immediately- HOWEVER- a new problem arose. It idled perfectly, I reved it, and turned it off again after only a minute or so since the air cleaner was off and I didnt want to suck anything bad into the engine-- BIG MISTAKE. :confuse:
Apparently there is a Learn Procedure for new CKP's that reprograms a timing aspect in the Vehicle Controle Module. Any time you replace a CKP you need to hook up a scan tool right after so that when you start it you can run the Learn Procedure. I did not do this and now the car wont start again- when I shut off the car it erased my previous timing codes so it will not start again until it learns a new DTC code..... I had to study the manual to find all this out :sick:
Anyways, I am soon to be back on the road again, I need to get the car to a real scan tool (I have a basic 1996+ one), but it still wont be that easy. Since the codes are erased I'll have to manually run the program, hopefully everything will work out fine--- just a WARNING to anyone else who has a similar problem-- if you change the CKP, be somewhere with a proper GM SCAN TOOL.
Again, any input is more than welcome-- Thanks
By my Chevy dealer shop new crank shaft position sensor can set the DTC (Diagnostic Trouble Code), i.e. lit up the check engine light but even when this happens the truck will run. Re-learn will then take care of this 'false' code.
I don't think your problem is with the crank shaft position sensor. In your earlier post you mention that you have plenty of spark and that you have plenty of fuel pressure in the fuel rail. Then when you pour fuel in the intake the engine tries to start.
Sounds like you have fuel injecting problems, i.e. injectors are not injecting fuel in the engine. Sounds weird when you say that after changing crank shaft position sensor it started up immediately but then would not again after you shut it off. Could there be some short of loose wire connection with the crank shaft position sensor that messes up other circuitry.
It almost sounds like your computer has gone bad as I think it controls injectors directly. That would be quite bad news as they can be costly to replace.
Check your engine ground wiring. Make sure engine is well grounded to the vehicle body and that the ground wire from the computer is well connected to the engine.
--Arrie--
Help is evidently needed.
JB
Cant believe it, turned out to be a bad fuel pump after all. Even though we tested 55+ PSI at the rail, it turned out sporadic. It wasnt holding a constant pressure, so the tests we got were completely misleading. What makes it worse is that it was replaced only about 8 months ago.
Even worse- DONT buy from "Global-Automotive" on Ebay. Stated in auction was a new AC Delco fuel pump warranteed for 1 year. After attempting to contact many times, filing with ebay, and finally contacting AC Delco, turns out he's selling counterfeit parts and its an open scam on Ebay, Delco is mounting a case against him and took my info as well as many others. Ebay will not suspend him since he generates so many sales (10,000 transactions + in about a year). So, im out my money.. and I'll have to pay more for a new pump- sucks
Thanks for the help- Ed
Hope I didn't take to long. Your compressor belt is comming of because of the adjustement spring. If you have the grinding noise it may be because your compressor is going out. I have heard from other writers that a lubricant can fixx this. But what a dealer is going to tell you is that you need not only replace your compressore, but also your need to replace your rear compresssor. This is wrong many times.A true mechincie will examine wheather or not enought material has gotten to your rear area. If it has not you will save nearly a thousand dollars. None the less the price the dealer charegs is much higher than a specialist.
Check rhe price from the dealer to an auto parts store. Then ask for the dealers wholesale dept. The price will be about $200.00 Less. Part only.
I have a 1997 Chevy Tahoe with 4WD and the 5.7-liter with the CSFI system. Getting a “check engine” light that is coming back with a P0300, Multi-port misfiring error code. I am having a problem getting this fixed and I am not able to pass the NJ DMV inspection. I can feel the rough idle when sitting waiting at a light or stop sign, but feels fine during regular driving and/or on the highway. To make a long story short I got a full tune-up (plugs, filters, etc.) and the # 2&4 fuel injectors replaced, but still getting the error.
I took it to the GM dealer and they trouble shoot it to a bad fuel pressure regulator and it is leaking fuel into the # 3&5 cylinders, causing the misfire. The cost will be $800+ to replace the regulator, replace the throttle body gasket and do fuel systems flush. What I don’t understand why is it only leaking in only two of the injectors as the regulator looks centralize? It sounds like the two mentioned injectors are the parts going bad. Any advice on this matter and if it sounds like it will take care of my problem. Thank you.
Go buy the pressure regulator and change it yourself.
The leak causing the problem on cylinders 3 and 5 I think means that fuel is leaking from the pressure regulator and dripping on the spark plugs around cylinders 3 and 5 causing a short on the spark plug boots and misfire. It would not make sense that due to pressure regulator going bad it would make only the injectors 3 & 5 to leak by. And a small amount of extra fuel in the cylinder would not cause a misfire anyways.
If it is dripping externally please have the pressure regulator replaces ASAP as it is a serious fire hazard.
Fuel system flush will not fix your problem. If it would, your vehicle now certainly would not run fine with higher speeds.
Do you have the aluminum heat shields around spark plug boots? They can cause a spark leak to engine ground if not installed correctly. Also, old spark plug wires / boots lose their resistance over time and cause more spark leak.
One easy trouble shooting step is to have your spark plug wires replaced. A set cost around $30 at car part stores (not dealer). Just make sure that the boots go deep enough on the plugs to minimize the spark leak. You can also replace the wires with high quality set that does not require use of the heat shields like I did. Set like this cost around $80, which is the cost of normal set from the dealer.
Another item that could be the problem is the crank shaft position sensor. They are notorious of going bad and a rough idle is one of the symptoms. Sensor cost is about &70 or so from the dealer. To change it I think your starter motor must come down as it is located behind the motor. At least in my '04 tahoe it is.
For the fuel system the only thing you need to do,in addition of changing bad pressure regulator, is to make sure your fuel injectors are clean. If you don't use injector cleaners in a regular basis it could be that injectors have build up deposits that do not allow a correct spray pattern and idle gets rough. With more throttle opening there is much more oxygen to burn and the injectors must open more. More open injector then woks better as the build up disturbs spray pattern less.
Run a few tanks of fuel with injector cleaners to see if it helps. Sounds simple but this could fix the whole problem and cost you only about $10 - $15 extra. This is what I would do first (after replacing dripping fuel pressure regulator).
About the throttle body gasket: Why do they want to change that? It certainly is not a problem source unless your throttle mounting bolts are so lose the gasket does not seal at all. I don't think that is the case.
If you do find help for your problem based on this post or if you don't would you please post back the results. This forum does not work if the other readers can't see the end result.
We all would appreciate that.
Thanks,
Arrie
new catys,muffler& exhaust
all new filters thru outincluding fuel&trans.
fuel presure test,ok
new plugs,wires,cap & rotor
trans.flushed & oil changed,and fuel cleaners used.
get the problem at high rev on highway,(65plus) engine gets rough,light gos on, smooths out,now getting hard to start takes two trys... frustrated!!!!! local mechs,are lost!!!
help please anyone!!!!!!! :confuse:
need help bad..... :sick:
thanks in advance!
Arrie
When you say that everything goes dead when the car stalls, what do you mean by that?
If everything electrical dies then it almost for sure means your battery shorts out. For example, if your radio dies at the same time why would the problem be the cars computer? The radio has nothing to do with that.
Arrie
I have 2003 Tahoe Z71 with 99000 miles on it. I have kept it in GREAT condition, oil changed every 3-4k miles, all the services done on time, tires rotated etc etc.
In the past 2 weeks my car has been idling rough, almost shaking at about 300-500rpm. It usually only happens when I have it in Park or Neutral. Recently it does it when I'm stopped at a light or just started the car and waiting to warm up a bit.
I brought it in to the dealership (yeah, I know) and they said it was the Throttle Positioning Sensor so they replaced it, in addition to all the spark plugs, air/fuel filter and spark plug wires. 2 days after getting it back, it started doing it again.
My check engine light came on the other day . They ran the computer and found the following codes:
P0171
P0174
P0300
What is up here? PLEASE, someone help.
Thanks y'all
Alex
P0300 is a misfire code and perhaps could be caused by the condition setting the two first codes.
Could be a MAF sensor problem, i.e. mass air flow sensor sees less air flow than actually enters in the engine. This can happen when the sensing wires in the MAF get dirty.
MAF can be cleaned but I'm not sure what to use. Them small sensing wires are so tiny. Perhaps you want to replace the MAF. It cost about $150. I replaced mine as I think I had a intake air temperature problem, which is built in the MAF.
Arrie
oh wait, i can think of a way the the computer has to do wiht the radio...if the brain controlls all the electrics, and the radio is electric, wouldnt that mean that if the computer is messing up then the electronics mess up???
Also, I don't think driving lights are either. There are other 'brains' for these.
If I was you I would get a new battery just to rule it out as a possible problem source. A good battery can be purchased for about $60 so it is not a huge loss even if it would turn out not to be the problem.
Batteries can really mess up the car and be intermittent problem. They are also difficult to diagnose when it is an internal problem with the battery.
Of course the problem could be the PCM but it sounds weird that all electronics goes out when the car stalls. Problem with the PCM should not kill all electric power.
Arrie
The guys at the dealership just keep telling me that they're "doing some research on it".
Any hints on replacing one?
Any other thoughts, feel free to keep 'em coming.
Thanks for your help man. 'preciate it!
Alex
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Item#: NECMAF68411
Price: $140.99
tax and shipping not included
"
Before you go to buy one you could try to clean it as it is very easy to remove from the intake air duct. Buy some spray grease solvent with no oil in it. I guess they are alcohol base chemicals, the kind electrical component workers use. Sorry I don't know any brand names here.
As you can see in the picture you attached those 3 small wires are so tiny you would not want to actually touch them.
The built-in intake air temperature sensor is that 'hump' on the rim at 5 o'clock position in the picture (right at wire harness connector).
The problem you have could also be temperature reading problem as it together with MAF signal tells the PCM how much oxygen flow you have going in the engine. If temperature is reading way too high it keeps your engine running lean.
The problem could also be bad connection at the wire harness causing wrong readings. Simple disconnect and re-connect maneuver can also help.
For diagnosing these issues I purchased a Car Chip from Auto Zone. It is a data logger you connect to the OBD II port in the car and you can record some variables as you drive and then analyze it in a PC computer. I think it cost about $100. For example the intake air temperature is one of the variables you can monitor.
Arrie
Let you know what happens.
Alex
but is it impossible for the battery to be shorting out the computer, and possibly destroy it?
also, if say it wasnt the battery, what else could it be?
Arrie
i told him he needs to do it very quickly
Here's an alternative:
http://www.trueflow.com/product.php
Be aware that most of these CAI kits state up to 10+ hp gain, the ones I've seen that document it show the gain at hi RPM where most of our driving is not done.
Carryover of oil mist...small droplet sizes in the 1-10 micron diameter size has always been a problem using this technology.