I have a 1991 S15 GMC Jimmy 4x4 (4.3L V6), and it is running perfectly... for about 30-45 seconds :-(
On a cold start, the engine purrs along and no problems are detected. After about 30 seconds though, there is usually a preliminary half-second stall, that the engine recovers from. Then about 15 seconds later, the engine dies. Attempts to restart fail, usually just flooding the engine with no sounds of even trying to fire.
To correct this, I have tried the following:
- New spark plugs/wires
- New distr. cap/rotor
- New air filter
- Test ignition coil resistance according to Chilton - test SAT
- Test pickup coil resistanve according to Chilton - test SAT
- Test MAP sensor, disconnected..no change
- Read ECM codes, none (just the 12 "all good" code)
I'm kind of at a loss now. I am getting a nice (perhaps too nice?) spray of fuel into the throttle body when it won't start, and the only thing I can think of to do tomorrow is to test each plug for adequate spark when it won't start.
Since the engine runs perfectly on start up, I'm suspecting "something" cuts or diminishes the spark, or increases the fuel mixture too much, when the system goes into normal idle mode. Either that, or something in the input voltage to the ignition coil is flakey(like the switch/wiring), and cutting out when the system is warming up. Any other ideas?
I shudder to think it may be something in the ECM itself...although there aren't any codes coming out of it, so I'm hopeful there.
Any help, here or in email, would be greatly appreciated. I'm kind of under a time constraint with this, as I wanted to take the family up to Canada for the holidays, and the weather up there is calling for my
4x4...Thanks! joe snipped-for-privacy@charter.net