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High idle when first started?

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Most likely it is the IAC. You need to remove the throttle body, take the IAC and TPS off of the throttle body, clean it REALLY well, clean the IAC shaft seat, and then reassemble everything. You will have to set the TPS back to proper specs when you are done. CLICK HERE for the how-to on the TPS adjustment.


If that doesn't fix it, then the IAC is probably going bad.

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Has anything changed with this vehicle before the problem arose? I mean have you changed or altered anything recently?


A manifold vacuum leak will also do this BTW...


True, and I had an issue where I changed the battery cables, and moved the ground to a different spot, which caused a severe high idle problem on mine.

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My 87 4.0L would do this all the time was driving me crazy constantly blipping the throttle trying to get it back down, was like constantly on the choke mode, sometimes would go back down. Once I replace all the fuel injectors with new 4 port (instead of 2 port) idles like a dream, gas mileage improved, and more power! :cheers:

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