I have a 2001 GMC Jimmy and my mechanic can’t figure out what’s wrong with it. It stalls and sometimes dies out when it heats up. The problem is worse in warm weather. So far they have replaced 7 mass airflow sensors, replaced 2 fuel pumps,tuned it up, fixed an evaporation leak, replaced the computer chip and more. It runs fine until it warms up. Then is stalls, especially at highway speeds. All filters, hoses and belts are OK. The car is still under extended warrantee. The computer codes keep saying fuel pump, mass airflow sensor or, the case now, nothing. The dealer I went to said he couldn’t help without computer codes and actually said I had to get stuck on the side of the road before he could help. The problem is over a year old.
with no codes, you have to do an on the spot test to find out if it is a spark problem or a fuel problem. Next time it dies, open the hood, get out, pull the center lead from the distributor cap, crank the engine and see if you have a bright blue spark when you hold the cap close to the terminal post. If yes, you have a fuel/air supply problem, if it is yellow or there is no spark jumping the gap between the terminal post and the end of the lead, you have an electrical problem in the spark supply (coil or igniter most likely). Some new vehicles you can no longer do this test, just one more wonder of modern engineering.
Thank you for the advice. I will give it to my mechanic tomorrow. He is keeping my car to drive home to see if it is still stalling. I’ll post the results here.
You might also have him check for a faulty crankshaft position sensor. GM’s are notorious for having these fail causing your problem.
Tester
Thanks to Ignoramus and Tester for quick replies, but the mystery still continues. I just came from my mechanic who drove the care again, and it starts to die out when it gets warm. He has replaced the coil, crankshaft position sensor as well as the other stiff (2 fuel pumps, 7 mass airflow sensors - all with AC-Delco parts). He lifted the carpet and did a complete check of the wiring. He also checked the fuel pump relay and drove with a meter on it. I still don’t know what is going on. If anuyone has any other ideas, please let me know.
The problem points to a control module problem. As the module heats up the engine dies, when it cools down it runs again until it heats up.
Here are some important questions for you to answer. Does the engine restart when it dies? Will it restart after it sits for a while? Has anyone actually checked for spark when it is acting up?
If it doesn’t restart then that is the time to check it out for spark and fuel.
Hi Willey,
Thanks and I will talk to my mechanic about it. He did have an expert replace the computer chip and reprogram it. I don’t know if that is what you mean by a control module. It does restart when it dies, but it runs rough at first. When it cools down, it runs better for a while, but as soon as I drive it for 30 minutes to an hour, it starts to hesitate and eventually stall.
The IGNITION control module is a separate component from the ECM.
Often when these tough cars presents themselves you need to go up a notch in the ability and experience of your mechanic. The first thing that strikes me is the number of mass airflow sensors,what was the reasoning with this path?
When the car does die (or start to die) is a stratagey being employed to logically move down the troubleshooting chart or is there a application of effort in a “all I have ia a hammer, so all I see are nails” approach? New man with more experience is needed here.
Hi oldschool and thanks,
I also questioned the mass airflow sensor changes each time it was done. It seems the computer kept indicating that was the problem, but it just doesn’t make sense that every one of them went bad unless there was another problem causing that to happen. I am reluctant to take it to another mechanic since all everybody knows these days is how to read the computer codes. In this respect, the dealer was the absolute worst. If I knew of a new man with more experience, I might try. I’ll keep results posted here.
Too bad GM doesn’t offer a service like this with all their BS Mr. Goodwrenches.
My mechanic ordered the Ignition Control Module and will install it today and drive it home. I hope this is it.
The ignition control module was replaced on 7/2/10 and I drove the car on 7/3. The car is still doing it. It starts to die out after 30 minutes to 1 hour of driving, then it’s OK until it warms up again. It will die out if I try to give it gas. Does anybody have any other ideas besides the mass airflow sensor, fuel pump, tune up, new set of wires, fixed evaporation leak, replaced computer chip, crankshaft sensor and ignition control module?
Thanks
I can’t begin to count the number of times a good man got stuck on a car,went to lunck and let his buddy take a look,and an asnwer was found. Sometimes this does not work as both mechanics get stumped. What it is is you dont want the first mechanic spoiling the results from the second. There is nothing wrong with backing away and letting someone else take a look, unless it gets to be an everyday thing.