Excessive Idle RPM - Need advice
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Northstar Engines and System Technical Discussion Discussion, Excessive Idle RPM - Need advice in Cadillac Engine Technical Discussion; My '96 Seville STS has, with increasing frequency, begun to idle at RPMs between 1000 and 2000. Revving the engine ...
  1. #1
    larryntripp is offline Cadillac Owners Member
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    Excessive Idle RPM - Need advice

    My '96 Seville STS has, with increasing frequency, begun to idle at RPMs between 1000 and 2000. Revving the engine does not get the idle to drop down to normal levels. I've given the linkage a cursory look and couldn't find any mechanical hangup, nor while idling at high speed could I get it to drop down by hand manipulating the throttle cable from under the hood. Any ideas on what is wrong or how I can troubleshoot? Thanks in advance.

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  3. #2
    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: Excessive Idle RPM - Need advice

    Vacuum leak or IAC died.

    Get a can of carb spray and hose all the rubber and plastic tubing you can find. Also spray around the base of the intake manifold, as sometimes the silicone dries up a bit and lets in some air. If the idle changes you've found your leak.

    It also can be something like a leaking brake booster, but less likely.

  4. #3
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: Excessive Idle RPM - Need advice

    Another possiblity is the TB. When is the last time it was cleaned? Could be very dirty and having the throttle plate hanging up a bit.

  5. #4
    danbuc's Avatar
    danbuc is offline Cadillac Owners Connoisseur
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    Re: Excessive Idle RPM - Need advice

    Did you check for any codes yet? When the TPS sensor in my car went it caused the throttle to stick like that when the weeper arm inside would get caught on a loose tab (it's just a potentiometer inside). I had two TPS codes as well.

  6. #5
    larryntripp is offline Cadillac Owners Member
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    Re: Excessive Idle RPM - Need advice

    Likely appears to be a gunky throttle body. I disasembled down to the TB, and gave it a good cleaning with carb cleaner and toothbrush. A short test drive showed no idle rpm problems. Tomorrow's commute will confirm. Thanks for the advice.

  7. #6
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: Excessive Idle RPM - Need advice


  8. #7
    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: Excessive Idle RPM - Need advice

    ^--- Always done in by the assumption that people maintain their cars.

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