Pontiac Repair: Engine dies and stalls in gear, maf sensor, coolant temp

Question
QUESTION: Hi i have 1996 Gmc safari van with 4.3 six cyl. My engine dies/stalls in gear backing out the drive way no check engine light.i replaced fuel pump,fuel filter and crank sensor.fuel pressure stayed at 50 to 60 psi never drop while engine stalls and dies.Need help

ANSWER: Hey Jeff:

well a few things to look at here. #1 that engine needs over 55 PSI of fuel pressure to run so if it drops below that it has the potential to stall it needs that much pressure to unseat the pottet injectors. If this only stalls on a cold start first thing in the Am you could have a bunch of things happening here. A coolant temp sensor that is reading wrong. I build up of carbon on the intake valves making the engine run lean on a cold start (very likely) especially if it has a lot of miles on it and when it restarts it runs okay. A couple of cans of GM TOP ENGINE cleaner can help this out and a few bottles of Chevron Techron injector cleaner run through the van added to the gas tank. A dirty throttle playe and bore or a dirty Idle air control valve.. Does this have any other symptoms like a pinging when hot under load or surging issue at a constant enegine speed? those could be related to a stretched timing chain and a distrubutor cam sensor timing that is off due to the chain. A dirty MAF sensor would be the last guess. and again these are all guesses but likely causes to waht is going on here. Good luck :)


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QUESTION: You mention engine coolant temp sensor One thing i forgot to mention my engine fan come on in am start switch off,a/c &def off and engine runs fine no surging or pinging issue.thanks

Answer
The engine coolant fan runs on that van all the time it's belt driven. The fact that the engine will not stall with the A/c on is a sign of the engine can't take the increased load from the a/c running. I would look at the MAF sensor first.. That is the main load sensing sensor for the engine.. Also like I said about the throttle body and idle control motor.