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low, rough, surging rpm at idle after hot start

This is a discussion on low, rough, surging rpm at idle after hot start within the General Help forums, part of the LSx Technical Help Section category; hello, having a caprice/statesman 2004 ls1. problem is when starting car while it is still hot from the previous start, ...

  1. #1
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    blonde
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    low, rough, surging rpm at idle after hot start

    hello,
    having a caprice/statesman 2004 ls1. problem is when starting car while it is still hot from the previous start, the rpm reading goes as follows. starts at 1000, then a few seconds decreases beyond the normal 700-800 to nearly 500, at that point the engine shivers, and if you press on the gas while in drive it will not produce power to move the car.. i would wait for a minute and the rpm would suddenly jump up from 500 up and down quickly a few times, stabilising at the normal 700-800.. then i can drive normally. other than that it is very good in all aspects..

  2. #2
    TunedbyFrost.com Tuner Frost's Avatar
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    The IAT sensor is in a bad spot and is getting heat soaked when the car sits for a short period and is restarted (like stopping at a gas station). With it reading falsely hot, your mixture is lean, that's why the engine is weak.

    What platform are you using to tune with?

  3. #3
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    blonde
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    aha, makes much sense..
    anyway, i forgot to mention that while this happens the engine check sign would come on.. but that is just a consequence.. where is the iat sensor located ?
    the ls platform

  4. #4
    TunedbyFrost.com Tuner Frost's Avatar
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    I mean what tuning platform as in which tuning suite.... this is the TUNING section

    The SES should not be coming on though. Without the scanner in a tuning package, our ability to trouble shoot is greatly hampered.

  5. #5
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    blonde
    2004

    i dont know info about the platform or tuning.. as i havent come accross that..
    anyway, while this low rpm shivering happened earlier i poured water over the stem of the intake (maf, iat) after which the engine self corrected (rpm). i will probably add insulation instead of relocating.
    thank you,

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