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Buick Forum: 2.5L 1992 Buick Century - high idle problem
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  1. #1
    Triple's Avatar
    Triple is offline Buick Newbie My Buick(s): 2004 Park Avenue & 2000 Century
    Join Date
    Nov 2014
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    2.5L 1992 Buick Century - high idle problem

    Experiencing an odd high-idle issue with my 1992 2.5L "Iron Duke" Buick Century Wagon. The colder it is, the more pronounced the problem, but it occurs to some extent at all temperatures.

    Idle is very high upon initial start-up. Stabbing the accelerator will drop rpms some but certainly not into the normal range. Idle speed is more acceptable once in gear and/or at operating temp, but it's always higher than it should be no matter the circumstance. Fuel economy has dropped considerably and there is a new odor from the exhaust that wasn't there before the problem manifested.

    The car has just 42K original miles and had a very thorough tune-up less than 3K miles ago. It did, however, sit in storage last winter for close to six months.


    Also: recommended brand / part no. for Iron Duke valve cover gaskets? I went Fel-Pro at the time of the tune-up and it started leaking again less than a year after installation.

  2. #2
    Join Date
    Nov 2015
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    Re: 2.5L 1992 Buick Century - high idle problem

    Not too familiar with the "Duke" but some things I would look at would be vacuum leaks(pcv, brake booster, lines etc), sticking plates or cable at throttle body, loose throttle body and I would look into an issue with your idle/air bypass which is used to raise idle at start up. A check for codes would be my first step.

    I always had good luck with Felpro gaskets. I just stay away from the old fashioned cork gaskets some offer.Make sure you have a valve cover free of distortion. Most people over torque the bolts and end up with continued leaks.

  3. #3
    ServantToTruth is offline Junior Member My Buick(s): 2000 Century, 2003 Century, 2004 Rendezvous
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    Feb 2017
    Louisiana & Mississippi
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    Re: 2.5L 1992 Buick Century - high idle problem

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    I agree with everything the previous poster said. I'm not very familiar with that specific "Iron Duke" either. When applying torque to the bolts, I recommend that you be a bit conservative. I have two intake plenums that are cracked in a corner near a bolt hole after being torqued to spec following the exact recommended procedure. They led to intake leaks that were hard to track down at first. Other than that, then maybe they were defective gaskets? Fel-pro are usually great (the best imo) so idk.

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