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High Idle YJ

Discussion in 'Wrangler YJ (1986-1995)' started by PremiumRedYJ, Apr 22, 2019.

  1. Apr 22, 2019 at 12:52 PM
    #1
    PremiumRedYJ

    PremiumRedYJ [OP] New Member

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    Clay
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    91 Red Wrangler YJ
    So I have a 91 YJ with the 2.5, I’m a new Jeep owner and this is my first one. I’m not new to cars in general but this thing has a very high idle. When you start it, it’ll stay at 2000rpm the whole time no matter what gear you’re in. I’ve checked for vacuum leaks and have replaced some hoses and still to fix. I cleaned the throttle body, put a new throttle body gasket on, cleaned IAC valve, and replaced TPS. Changed air filter and cleaned intake tubing. This thing still to no avail is idling at 2000 and I can’t seem to track it. I pinched the breather hose for the brake boost and it dropped to 1500 but still too high of an idle. Any suggestions??
     
  2. Apr 22, 2019 at 12:53 PM
    #2
    Prerunner1982

    Prerunner1982 Well-Known Member

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    Was in intake recently replaced? Sounds like an intake manifold to head leak to me.
     
  3. Apr 22, 2019 at 1:28 PM
    #3
    PremiumRedYJ

    PremiumRedYJ [OP] New Member

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    I’m not sure. It’s new to me, haven’t had it more than a two weeks. I sprayed carb cleaner all around the intake manifold to listen for idle change but it didn’t stutter a bit.
     
  4. Apr 22, 2019 at 2:09 PM
    #4
    Prerunner1982

    Prerunner1982 Well-Known Member

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    Let me rephrase my previous statement, was the intake recently removed and put back on such as in an exhaust manifold replacement?
    It's a pretty common issue to not get the intake seated correctly/completely.
     
  5. Apr 22, 2019 at 2:18 PM
    #5
    Jim Beam

    Jim Beam Well-Known Member

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    Fuel Injection, Dana 44s, T18, 4.10s w/lockers
    Assuming you have a throttle body injection, a vacuum leak will cause an idle increase. That decrease you get from pinching the brake vacuum line might be from a leaky brake diaphragm. If you have a vacuum hose going to the distributor, do the squeeze test on it for a bad hose or vacuum advance.
     
  6. Apr 22, 2019 at 3:15 PM
    #6
    PremiumRedYJ

    PremiumRedYJ [OP] New Member

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    It’s multi port injection. The intake has not been taken off since it’s been in my hands. This one doesn’t have any vacuum hoses going to the distributor.. I recently order a new exhaust manifold for it and will be replacing the old one in the coming days. But I haven’t disassembled any of it yet.
     
    Prerunner1982 likes this.
  7. Apr 25, 2019 at 10:37 PM
    #7
    PremiumRedYJ

    PremiumRedYJ [OP] New Member

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    91 Red Wrangler YJ
    After spending some time and $$ I got the vacuum leak gone for the most part. Have a new intake gasket, all the hardware, torqued in the correct sequence and correct spec. Put a new booster on and everything seemed good when I first started it. Then it started to surge. Jumps from 1000-1500. I’m guessing it’s a sensor issue, but I’m not into spending any more money on sensors. Anything else I should check for?
     
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