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Thread: Rough idle when motor gets warm?

  1. #1
    Join Date
    Mar 2012
    Location
    Eastern Ky
    Posts
    6

    Default Rough idle when motor gets warm?

    I hav a 90 xj 4.0 5 speed,it isles smooth as silk until it warms up thn has a pretty bad miss. I can Giv it fuel an it smooths out. It's only at low idle wn warm. Any ideas?

  2. #2
    Join Date
    Sep 2009
    Location
    Chico, CA
    Posts
    29,847

    Default Re: rough idle when motor gets warm?

    When was the last time your O2 sensor was replaced?
    230 hp 4.3L Chevy
    Built 4L60E with manual lockout
    Atlas 4 speed
    Griffin radiator
    On board air
    Warn 9.5ti on custom bumper
    7.5" RE front and bastard pack rear on custom long arms
    30 gal gas tank
    lockers
    And a bunch of other stuff

  3. #3
    Join Date
    Sep 2009
    Location
    On my mountian NOR CAL
    Posts
    1,879

    Default Re: rough idle when motor gets warm?

    its a renix system,clean the iac (idle air control) then check the map sensor on the firewall be sure it is hooked to the TB and is getting vac. rough idle after she warms up means that when the computer releases control of the rig to the sensors one of them is not working correctly. I also agree with Steve on the O2 sensor , but will add, get a good one, factory if you can afford it ,XJ's dont take well to the aftermarket variety
    Aint got no whistle, don't belch out smoke, but my V10 aint no joke !!!

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