1. #1
    otis60's Avatar
    otis60 is offline Junior Member
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    High Idle 3000 to 4500 rpms

    I have a 99 TJ. The engine was running fine until I replaced the exhaust manifold. Now when I start in it is idling at 3000 to 4500 rpms. The throttle is not stuck open it works fine. I had to disconnect the fuel line to the fuel rail I did not remove the injectors from the intake. All vac hoses are fine no cracks or leaks . need help what is causing this to happen?

  2. #2
    k-2's Avatar
    k-2
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    Re: High Idle 3000 to 4500 rpms

    knee jerk answer- there is a vacuum leak.
    PCV/CCV, brake booster va lnes?
    try the old school carb spray trick to locate vac leak - intak manifold?
    tell us which eng. 2.5 4.0 ? Why new manifold?

    THe system would have a code SO a scan would be a start - even if light is off post codes
    Last edited by k-2; 08-11-2017 at 07:25 AM.

  3. #3
    otis60's Avatar
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    Re: High Idle 3000 to 4500 rpms

    IT is 4.0. I scanned it no codes at all. I replaced the exhaust manifold because the flange to the header pipe rusted off.

  4. #4
    k-2's Avatar
    k-2
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    Re: High Idle 3000 to 4500 rpms

    did you use a scanner? That rpm I would expect code .


    Use the old school spray trick for a vac leak, you did replace manifold gaskets ?

  5. #5
    otis60's Avatar
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    Re: High Idle 3000 to 4500 rpms

    yes new gasket.

  6. #6
    superj's Avatar
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    Re: High Idle 3000 to 4500 rpms

    you have a vacuum leak somewhere
    no more jeeps at this time. next time it will be a cj with a v8

  7. #7
    otis60's Avatar
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    Re: High Idle 3000 to 4500 rpms

    Found the leak the #2 intake flange on intake manifold.

  8. #8
    JPNinPA's Avatar
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    High Idle 3000 to 4500 rpms

    Glad you found it.

    When you replaced the exhaust you had to loosen the intake. There are two locater pins on block to marry with the intake. So if you loosened it enough the intake may have slid on top of the locator pins. Just be sure you look to make sure the intake is not on the pins but the pins are in the holes. If you just torque down on the bolts you run the risk of bending the intake and more leaking will follow.


    Also are you aware there is an order to tightening the intake and exhaust bolts. And these bolts stretch so you only get a few tightenings out of them and too many ft-lbs of torque will stretch them.


    Regards,
    JPNinPA

    Sent using TapTalk
    Last edited by JPNinPA; 08-11-2017 at 07:35 PM.
    "Never look down on anybody unless you're helping him up" - Jesse Jackson

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