Mechanics

CAR IDLES REALLY ROUGH AT START UP UNTIL WARMED UP

1999 Pontiac Grand Am • 113,000 miles

My 99 grand am runs really rough until it warms up and then is fine. Lately when I start it, it sputters and dies. If I punch the gas quickly it comes to life. There is a fuel smell with the exhaust. I have unplugged the maf sensor and there is no change and it is clean. Egr valve seems to be ok and the passages are not blocked. I have sprayed all over with carb cleaner and haven't found any vacuum leaks. I'm at a loss! It's the 3400 engine.
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Grandamkc
November 9, 2013.




Pull the vacuum line off the fuel pressure regulator with the engine running and see if any fuel comes out of the regulator port.
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Wrenchtech
Nov 9, 2013.
Pulled the vacuum line from regulator and ran for five minutes. No fuel coming out

Tiny
Grandamkc
Nov 9, 2013.
OK, that means it's good. You are going to need a high end scan tool to analyze the sensor data when this is happening to paint a picture of what is happening inside the engine before you can determine why it's happening.

Wrenchtech
Nov 9, 2013.
Ok this time it threw another code. A po0133 for 02 sensor bank 1. Any ideas?

Tiny
Grandamkc
Nov 9, 2013.
That slow response in that sensor and it should be replaced but I expect you have more problems than that.

Wrenchtech
Nov 9, 2013.
Got it fixed! Put a match in the gas tank and now no more problem! Lol

Tiny
Grandamkc
Nov 9, 2013.

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