1990 Ford F250 5.8. Idle issues

Discussion in '1987 - 1991 Ford F150, F250 and F350 Truck Forum' started by SwervinErvin, May 26, 2018.

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  1. SwervinErvin

    Idling fast. Have replaced:
    Idle Air Sensor
    MAP Sensor
    Idle Position Sensor
    Have cleaned the throttle body, checked for vacuum leaks.
    Now idles fast, or dies, or throttles up and down very fast.
    What else could be causing my problem?
     
    SwervinErvin, May 26, 2018
    #1
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  2. FTZ HAIC Staff Member Oregon Chapter Founding Member

    Have you checked for any codes in the PCM?

    Look to see if the PCM is throwing code 41. Fast idle usually means a vacuum leak somewhere, do a smoke test if you haven't already just to double check this. Look around the intake manifold during the smoke test for manifold gasket leaks.

    Check the EGR valve for proper operation.

    Check fuel pressure and the fuel pressure regulator.

    Throttle position sensor.
     
    FTZ HAIC, May 28, 2018
    #2
    SwervinErvin likes this.

  3. dustybumpers Article Contributor Founding Member

    Like Ken said, you still have a vacuum leak somewhere.
    You also need to check the IAC ( Idle Air Control valve)
    It could be loaded full of carbon
     
    dustybumpers, May 28, 2018
    #3
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