Question about 1999 Pontiac Grand Prix

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Rough idling in a 1999 Grand Prix GTP

My car just passed 200km and it seems like everything is going!! My car idles rough, usually between 500-1200rpm. It started a few months ago off and on and has progressively gotten worse. It is to the point now that the car will not start and stay running unless you give it some gas when starting it, and hold it at 1500rpm for a couple mins. Sometime it will not stay running, other times after a few mins the rpm's will come up to a normal range. And this again, doesn't happen every time I start the car, but times than not now though. Any ideas????


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  • Anonymous May 04, 2009

    i have somewhat the same problem. rough idiling, engine light came on, had code checked said misfire at #4. said i needed a tune up so i did that when i picked the car up he said i had no compression in #4,expensive repair, so i took it for a second opinion and the said the motor is fine, it has compression and fire but they dont know why its still missing, so next step he said it probally needs new head gaskets, but hes not sure, but he cant find nothing else wrong. another expensive repair $1000. and hes not sure if thats the problem. can anyone help!!!!

  • Dennis Yachimec May 11, 2010

    Try putting new spark plugs in it.



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If this problem doesn't happen every time i would not only change plugs but wires as well.The wires can move if they are loose or even heat damaged and interrupt the spark. If this doesn't help it sure won't hurt. Next look at the oxygen sensor and change the pcv valve. Then i would move unto cleaning/replacing the MAF sensor and possibly the throttle position sensor too. It sounds like you need a good tune up thats all.

Posted on May 03, 2009


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