Stumbles, stalls and wont start....

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Old 05-15-06, 05:19 AM
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Stumbles, stalls and wont start....

I am working on a 1988 Pontiac Grand Prix 2.8 litre that hesitates and stumbles real bad upon acceleration between 20-30mph, stalls out when hot and is hard to restart. Fuel pressure looks good and the car was recently tuned. It looks like it may be a faulty MAF sensor since it comes up with a code 34, also and it feel like its running a bit lean when you blip the throttle.

When it wont start though, if I disconnect the harness connector to the MAF sensor the car still wont start. If the sensor was in fact bad, wouldn't unplugging the MAF sensor cause it to start because the ECM will use default values instead of the "bad" ones coming from the defective MAF sensor?? Any assitance would be greatly appreciated.
 
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Old 05-15-06, 07:04 AM
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While testing the fuel pump pressure when the car wont start, pressure is at 42psi while cranking. While the car is running, pressure is at 38psi.

When I turn the key to ON, but not cranking though, pressure is at 38psi for a few seconds while the fuel pump energizes, but then pressure drops down to zero after that. Is it supposed to drop down to zero while the key is set to ON?? If not, any ideas?
 
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Old 05-15-06, 05:33 PM
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Out of curiosity, is your car just getting into second gear, under more of a load condition, when this occurs in the speed range? If so, maybe there is some kind of advance issue going on. I'm not sure. Just throwing something out there.

If you don't get a satisfactory answer here, you could do as I, and call up auto parts stores and pick their brains. Afterall, they sell the parts, like MAF sensors and everything under the sun, and many of these guys are good.
 
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