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Thread: Please help with eratic idle!!!!!!!!!!

  1. #1
    VIPERRACING is offline Cadillac Owners Member
    Automobile(s): Cadillac
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    Please help with eratic idle!!!!!!!!!!

    Hi guys, I have a 99 sts that has an eratic idle or hunting idle(up and down)after its warmed up and sitting in traffic. It doesnt do it when I turn on the a/c. Any help would be appreciated. Thanks, Tony.


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  3. #2
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
    Automobile(s): White Diamond '03 DHS (with DTS floor shift)
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    Re: Please help with eratic idle!!!!!!!!!!

    Sounds like a vacuum leak, but start with a good TB cleaning if you haven't done it recently.

  4. #3
    VIPERRACING is offline Cadillac Owners Member
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    Re: Please help with eratic idle!!!!!!!!!!

    Quote Originally Posted by Ranger View Post
    Sounds like a vacuum leak, but start with a good TB cleaning if you haven't done it recently.
    It only does it when im stuck in traffic. I turned on the a/c to see what would happen and it kept a steady rpm. I was thinking that it was the egr. Could it be the egr valve?

  5. #4
    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
    Automobile(s): 2002.5 F55 STS - 67,500 miles, 2014 Explorer XLT FWD
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    Re: Please help with eratic idle!!!!!!!!!!

    The fix is probably to: Do a good throttlebody cleaning. Do a good EGR valve cleaning. Pull the engine cover and do a thorough search for vacuum leaks.

    If turning on the A/C temporarily cures the hunting, then the problem may be an erratic ISC system: the A/C ON command also increases idle speed slightly, so that function may either move the throttle butterfly or increase idle air just enough to "cure" the problem.


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