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high curb idle, wants to go at a stop light

Old 11-20-2016, 12:20 PM
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Join Date: Aug 2016
Location: TEXAS
Posts: 29
Model: Grand Cherokee
Engine: 5200 cc
Question high curb idle, wants to go at a stop light

My sixteen year old son has a 94 ZJ with the 5.2 , truck wants to go forward at stoplights and seems a little faster than is should be. is there a way to reduce the idle? Tachometer says 7 or 8 not sure if that is accurate. Any suggestions? Vacuum leak maybe?
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Old 11-20-2016, 09:45 PM
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Join Date: May 2015
Posts: 577
Year: 1994
Model: Grand Cherokee
Engine: 5.2L Magnum V8 220hp 285ft-lbs

Unintended acceleration?

The idle is supposed to be controlled by the IAC, a stepper-motor-controlled pintle that changes an air aperture to the intake plenum. It should lock the idle RPM, the FSM says 500 to 900 RPM.

The IAC testing requires a DRB test tool. It is easy w/ the tool, just select the desired RPM and it will lock onto the correct RPM.

It might be that the IAC is not operating properly.

Yes it is possible that an air leak is causing problems.
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