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GM Tech (Cam)
GM Tech (Cam), Pontiac Technician
Category: Pontiac
Satisfied Customers: 2374
Experience:  GM Grand Master Technician 2007. 14 years experience.
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Pontiac Gran Prix: Note, vehicle has new plugs and wires, new

Customer Question

Note, vehicle has new plugs and wires, new fuel pump and filter; approx 190 K miles. No codes. My 1999 pontiac gran prix with 3.1 engine has developed a starting anomaly. The motor spins with no difficulty; it trys to run, sometimes with success, but often requires multiple attempts. It seem that depressing the accelerator at the right moment allows the vehicle to start and run. Once started it runs smoothly with no hint of a problem. The fuel system pressure checks out with no problem. Achieves a pressure about 42 psi, drops to 39 after 10 minutes and holds above 30 for approximately an hour. Up until about six months ago, it started without touching the accelerator; generally on the first attempt. Not sure of exactly when, but mileage has dropped by 30%.
Submitted: 1 year ago.
Category: Pontiac
Customer: replied 1 year ago.
Why does my 1999 Pontiac Gran Prix with 3.1 engine have a difficult time starting? Recently it has begun to require depressing the accelerator to get the engine to continue running. Once stable the engine runs and drives fine.It may take two or more trys to get the engine running. Vehicle has 190K miles. Recently plugs, wires, fuel pump and filter have been replaced. Checked out fuel system pressure. Meets all specs. No engine codes are present. I have no worries with vehicle except start-up; I keep wondering if thsi will be the time it doesn't start.
Expert:  Jan Andersson replied 1 year ago.
Hi, Sounds like maybe its not getting enough fuel, despite the new fuel pump.You could confirm this by spraying starter spray or flammable carb cleaner into the intake as someone else is turning the key. If it starts right up, you'll know that it was not getting enough fuel. Then we need to figure out WHY. One common reason is a bad or dirty Mass Air Flow sensor (MAF). It measures how much air goes in the engine, so the computer can inject the right amount of fuel. When the sensor gets dirty, it starts reporting less air, so you get less fuel too. They can be cleaned with a MAF sensor or carb cleaner spray, but you can't touch the internal parts with anything, they are very sensitive. Spray liberally from 2" away. From both directions even. DO you have access to a code scanner that can show live data? Even if you don't have a check engine light on, the various sensor readings when the engine is running, could offer good clues, if something seems to be out of range. Is the check engine light on now?