I need help with an as yet undiagnosed engine problem with my 2000 Tahoe Z71. After driving the truck for 30 minutes or so and then turning the truck off and letting it sit for 30 min to 6 hours, upon restart the truck stumbles, misses and backfires when accelerating. The truck will not accelerate beyond 20 MPH. Afer about 30 seconds this behavior disappears and everything is normal.When thetruck sits overnight it does not display this behavior.This happens 80% of the time. Recently I had an incident where the above description occured but it also stalled and would not restart. After a few minutes it would restart and I could travel several hundred feet before it stalled again. It took me 1 hour to travel 3 miles home from the grocery store.
The truck has been examined by two Chevy dealers and the mechanic I have used all my life. No one has found the cause, although I have spent more than a thousand dollars at the Chevy dealer replacing injectors, regulators, etc.
I do not have a service manual so I do not understand what sensors affect ignition timing. To me a backfire implies there was a burn still occuring in the cylinder when the intake valve opened. I do not think an over rich intake charge is my problem because I do not see black smoke at the tail pipe when this is occurring. I suspect severly retarded timing. What do you think?
Assuming it is timing does anyone know what sensors give feedback to the ECM that affect timing(I am thinking of just replacing all the relevant sensors and maybe their wiring)? Does anyone have an online source that describes the sensors and ECM interactions?
Or any advice at all? I am at my wits end.

thanks,
pat

 

The timing is controlled by the computer on that car. But yes timing can affect it. How many miles do you have on it? It could just be a lose timing chain/belt.