Thread: Rough idle when car starts?

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  1. #1 Rough idle when car starts? 
    SE Level Member jjwalton77's Avatar
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    In the last month or two my car has been getting this rough idle when i start it up after driving it somewhat hard. The rpm's fluctuate from 1.5 to almost 0 for a good 20 seconds or so before it goes back to normal. The car wont do this if i really baby her on the gas, only when i open it up or go through stop and go traffic in town will it do this. Any ideas what it could be? Something like a fuel pressure regulator, or as simple as a vacuum lines disconnected?
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  2. #2 Re: Rough idle when car starts? 
    Turbo is the way to go. Fivefingerdeathpunch's Avatar
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    Maybe clean the throttle body and maf sensor with the correct cleaners, it might help.

    Checking over vacuum lines wouldnt hurt either.

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  3. #3 Re: Rough idle when car starts? 
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    When it runs rough, does your check engine light come on? Or has it just stayed on since its been doing it for a while now?
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  4. #4 Re: Rough idle when car starts? 
    SE Level Member jjwalton77's Avatar
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    the ses light has been on for awhile now from the bad seal by the gas cap. and im not sure how to clean the throttle body, ill see if there is a thread on here explaining it
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  5. #5 Re: Rough idle when car starts? 
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    Just remove your air tube that is connected to the throttle body, and use an intake cleaner. Personally I have always used BG products, they are the best. You can buy them at any auto mechanic shops that sell them, I noticed that my GM dealership sells them, but as always they will probably jack the price up on them, so try a auto mechanic shop first. As far as cleaning it, I turn the car on and spray it in the throttle body while reving throttle a little, dont try to over kill on the throttle just enough to keep the car from wanting to shut off, cause when you spray the cleaner it will want to die on you. Dont spray alot at one time either, just a couple of short sprays, then maybe give it alittle more. The spray is alcohol based so it dries very quickly.
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  6. #6 Re: Rough idle when car starts? 
    Turbo is the way to go. Fivefingerdeathpunch's Avatar
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    or, remove the MAF itself and unbolt the throttle body ( you'll want to buy a new gasket) and clean it that way with TB cleaner and clean the MAF with MAF cleaner.

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  7. #7 Re: Rough idle when car starts? 
    SE Level Member jjwalton77's Avatar
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    Just thuroughly cleaned the throttle body, and found that a vacuum hose that had a bad crack on it. Just put it all together and the car seems to idle much smoother, still not able to tell if it will do the whole rough start thing, but so far so good. Thanks guys!
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  8. #8 Idle is getting worse, need help! 
    SE Level Member jjwalton77's Avatar
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    I posted a couple weeks about how my idle was bad and i wasnt sure what was causing it, well i took apart and cleaned the throttle body, and found a tear in a vacuum line. I fixed the line and it ran well for a day or so, now its been getting worse, with the rpm jumping from 500 to 2000 while at idle and every once in awhile it will make the car stutter when accelerating. Any body have any ideas what's causing this? Fuel pressure stabilizer? If so, how would i go about replacing it?
    Thanks guys.
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  9. #9 Re: Idle is getting worse, need help! 
    GTP Level Member Impala131's Avatar
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    Hmm, my first instinct is to say MAF sensor. Got any codes? Get them scanned, look for a P0102.
    2003 Grand Prix GTP.... the journey begins again....
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  10. #10 Re: Idle is getting worse, need help! 
    GT Level Member t24moore's Avatar
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    Spray around your engine bay with carb cleaner, you may have a vaccum leak. The plastic hose that comes off the supercharger could be cracked somewhere. But like stated above do you have any codes?
    Comp Turbo 6765 T4-ST5-A2A IC-Ported Heads-Custom Turbo headers-80 lb inj-F-Body UIM and LIM-AEM WB, TEP trans w 1" chain and Circle D TC, Dual 255s, Bilstien Struts
    WHY IS EVERYONE SO OPPOSED TO DOING A COMPRESSION TEST TO TROUBLESHOOT PROBLEMS?
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  11. #11 Re: Idle is getting worse, need help! 
    Turbo is the way to go. BillBoost37's Avatar
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    I've merged your threads. That way people can easily see what has already been suggested and you don't end up saying "I tried that already"
    I drink..so consider that when reading my posts.

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