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2.5 high idle after 4.0 throttle body swap.

Discussion in 'Quitters' Club' started by GreenGhost, Apr 20, 2014.

  1. Apr 20, 2014
    GreenGhost

    GreenGhost Never give up!

    Linglestown, PA
    Joined:
    Apr 6, 2008
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    291
    So I went and swapped out the throttle on my TJ as described on a few of different forums. I reused all the 2.5 sensors hooked all the cables back as they should be and reset the computer. But the idle still won'tdrop back. I'm stumped. Anybody have any thoughts. Thanks.
     
  2. Apr 21, 2014
    hudsonhawk

    hudsonhawk Well-Known Member

    North Texas...
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    Feb 4, 2005
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    Are you sure the IAC is working correctly and not stuck?
     
  3. Apr 21, 2014
    GreenGhost

    GreenGhost Never give up!

    Linglestown, PA
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    I'm not sure. The IAC worked on the 2.5 tb before I did the swap. I was thinking that may be the culprit. It also takes a few seconds to drop down after letting off the gas pedal.
     
  4. Apr 21, 2014
    hudsonhawk

    hudsonhawk Well-Known Member

    North Texas...
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    1,937
    I am trying to remember if the 4.0 TB has any kind of butterfly valve adjustment. It may be open just slightly allowing more air to bypass and increasing the idle. That would also account for the slow return to idle after letting off the gas pedal.
     
  5. Apr 21, 2014
    hudsonhawk

    hudsonhawk Well-Known Member

    North Texas...
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    Did you use a new TB gasket when you put the 4.0TB on?
     
  6. Apr 21, 2014
    GreenGhost

    GreenGhost Never give up!

    Linglestown, PA
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    Apr 6, 2008
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    No, but I'm going to pull it off again to clean the IAC I'll put a new one then.
     
  7. Apr 21, 2014
    GreenGhost

    GreenGhost Never give up!

    Linglestown, PA
    Joined:
    Apr 6, 2008
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    291
    Cleaned the IAC sensor and installed a new gasket on the TB, it still idles high. I was doing some reading about the TPS and that could cause an erratic idle too if it's on the fritz, It had some of those symptoms intermittently before the swap I ignored them because they didn't happen often, so tomorrow I'l lswap out the TPS and see what it does.
     
  8. Apr 23, 2014
    GreenGhost

    GreenGhost Never give up!

    Linglestown, PA
    Joined:
    Apr 6, 2008
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    291
    I cleaned the IAC, replaced the TPS and installed a newTB gasket. Still having a high idle issue, but it doesn't jump around as bad as it used to. The new IAC should be here Friday and I'll see if that makes it better.
     
  9. Jun 20, 2014
    hunter_02

    hunter_02 New Member

    Joined:
    Jun 5, 2014
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    Mr. Ghost, I tried that swap on my '98 TJ a few years back. Ran like krap. The cure for me? Put the old throttlebody back on, but with a throttle body spacer. Did every thing I wanted it to do. Better gas mileage, more low end torque, better 'driveability', just an all-around happier Jeep.
    As my mechanic buddy explained it to me, it doesn't have as much to do with flow as it does to do with 'velocity'.
    Hunter
     
  10. Jun 21, 2014
    GreenGhost

    GreenGhost Never give up!

    Linglestown, PA
    Joined:
    Apr 6, 2008
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    291
    I ended up pulling it and putting the factory one back on couldn't get it to run right. Where did you find the spacer, did you use one for a 4.0?
     
  11. Jun 21, 2014
    hunter_02

    hunter_02 New Member

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    Jun 5, 2014
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    There are pricey ones on 4WD and QTec, but I just got a cheapy off of Ebay. And no, IIRC the listing was for a 2.5L
    Hunter
    Just did a search on Ebay. They have them from $36 delivered to over $100. Don't fall for the 'helix-swirl' krap.
     
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