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1998 Ford Expedition Question: idle surging

 

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Visitor, 4.6L V8, Warrenton, VA, November 24, 2010, 21:57

My 1998 Ford expedition has a surging idle when topped or in park. It will fluctuate between 400 - 1500 rpm. I have replaced the mass air flow sensor and the vacuum line coming from the PCV valve to the rear of the air intake manifold. There is no "check engine" light on so there is no codes to look at. Does anyone have any other ideas?

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  • Answer #1

    delane 72 garage and body shop November 24, 2010, 22:21
     Master

    clean throd body idle up to 800.rpm change fuel filter

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  • Answer #2

    DaveJHM November 24, 2010, 22:42
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     Master

    I would be looking at the idle air control valve, or a vacuum leak at the intake manifold, or something similar to that.

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    dr_music59538, November 25, 2010, 07:12
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     Rookie

    Could also be a Throttle positioning sensor or TPS going bad too I think my firebird needs either one of these checked on it too.

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