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EZ EFI 1.0 - idle 1200 to 1500 rpm

Discussion in 'FAST Support Forum' started by Jeep Guy, Mar 15, 2017.

  1. Jeep Guy

    Jeep Guy New Member

    Mar 15, 2017
    Thanks in advance for any advice.

    I have an EZ EFI 1.0 installed on a 4.0 L Jeep. I have never been able to get the idle to slow down to the selected idle speed.

    For example, when first installed, it idled at about 1000 rpm instead of 750 rpm, but otherwise ran o.k. Lately, the idle has been climbing and it now bogs with attempted hard acceleration.

    More information.
    IAC is showing 5 at idle speed 1200 rpm.
    If I increase the idle speed on the computer console to 1300 rpm, the IAC starts bouncing and the idle starts bouncing up and down until it stalls.

    When I run a new "tune", the TPM tuning prompts me to adjust the throttle position to a resultant rpm of 2200 rpm. When I turn the idle speed screw to the slowest setting, I am at 1200 rpm (IAC 5).

    So far, I have not found a vaccuum leak. What do I do next? Try plugging the IAC? Disconnect the O2 monitor. Check the throttle blades? Look some more for a vacuum leak? Check the wiring for "interference".

    Thanks for any advice on what to do next.
  2. gtsman

    gtsman Member

    May 30, 2014
    If your IAC is at 5 then it's bottomed out, ( closed ) 5 is it's lowest #. This sounds like either a vacuum leak, or your linkage is binding hanging the throttle open.
    Have you looked down the throttle bodies and verified that the throttle plates are completely closed? ( Engine off ).
  3. Jeep Guy

    Jeep Guy New Member

    Mar 15, 2017
    FOUND IT!!!

    There is an uncapped port on the back of the FAST efi. Hard to see, but I put my finger over it while I was cleaning the the throttle body. Started it up and put my finger over it, and the IAC came to life and the engine idle immediately went down to 750 rpm. I think it was installed this way :/ Thanks GTSMAN!!!

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