Been working on this thing about a week or so. Out of the blue car won't stay running at idle. Have looked at dozens of posts and YouTube videos. Still scratching my head. No check engine light, have sprayed the entire engine compartment down with carb cleaner trying to find vacuum leak, with no luck. Replaced throttle body, purge valve, maf sensor, and intake manifold gaskets. Checked with my solus scanner and everything seems to be in specs. What am I missing. Someone please help.

 

Did you perform a throttle body relearn procedure after replacing the throttle body?

does the vehicle start easily?

If you keep your foot on the gas, will the car continue to run indefinitely?

From a cold start, does the vehicle start at a higher RPM, then work its way down as it warms up, running just fine, then gets to idle speed and just stops?

Auto or manual? Regardless, will it idle in neutral? I'm assuming automatic.

 

I did not do a relearn. From what I have seen you have to let it run at idle for 10-15 minutes to do the relearn. It will stay running as long as I keep rpm's above 1000. Does not clear up.when the car gets to operating temp. No difference in neutral or park. Turning on any load makes it worse. Trying to put into gear to move vehicle is time consuming, with stalling and restarting to move a few feet. The vehicle is an automatic. Starts fine 3 out of 4 times, 4th time may take a few tries.

 

A GM relearn for this vintage was to block the wheels, put in 'D' and idle until the PCM cycles the fan. Takes a bit of time and it may stall. Just start it back up slip in 'D' and let it idle.

 

I had the same symptoms See pic as I replaced the module on the right side of the valve cover. It solved the problem, and it was cheap.

 

Okay it's me again. Still having the same issue. Have done the relearn, have replace coil pack and module. Still having same issue. Now doesn't even want to start. Cranks with no start. I have about lost my mind on this thing. Oh and still no codes, except when it dies it sets the communication code

 

How many miles on this car? If it has 150k plus I would check compression. This is a chain engine with a weak chain setup.

 

Has 180k on it. Already did compression check, all cylinders good. Did smoke test for vacuum leaks, no leaks.