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StanF 06-21-2013 03:29 PM

IAC - idle speed changes when unplugged?
I'm trying to track down the cause of my high idle (~1500 rpm). Nothing new - it's been the same as long as I've owned this Jeep (2.5L). I'm just getting around to trying to fix it.

Quick question...should the idle speed change when the IAC is unplugged? When I unplug mine, nothing happens

The plunger on my IAC cannot be screwed in/out or adjusted in any way, as I have read in other threads. It is locked firm, and is not threaded, as far as I could tell.

What I've done so far:
- checked for vacuum leaks by unplugging the vacuum lines individually at the manifold and blocking off the port. Sprayed TB cleaner around the intake gasket and TB gasket. No leaks found, but the MAP sensor didn't like being unplugged, so it would be the only "maybe".
- thoroughly cleaned IAC and TB
- changed TPS

Nothing has improved it so far, but maybe my tachometer is off? Subjectively, it sounds like the idle is high to my ears. I didn't want to spend $65 on a new IAC if its not the problem, but I'm out of ideas.

I have an old-style dwell/tach (alligator clip lead), which could be used to verify the tach reading. But am not sure how to hook it up to my Jeep's ignition.


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