High idle on 5.2 liter

My tow vehicle, '98 Jeep Gr. Cherokee 5.2 V-8 has less than 85k miles, is well cared-for, and lately in neutral at operating temp jumps to a persistent idle around 1100 rpm vs a more normal of some 700. You-uns experts: could this be the idle air control motor or the intake manifold air temperature sensor, or the crank position sensor, or?

Many Thanks In Advance.

First go to Advance Auto parts (or any auto parts store) and ask them to put their code reader on it. It's entirely possible that there's information which aren't important enough to throw the check engine light.

It's also possible the check engine light is "on", but the bulb is burned out.

This will eliminate both possibilities.

Thanks; my "Check Engine" light turns on during the light test upon starting motor, then light shuts off. Will run my Car MD scanner to see what it shows (forgot I had it!).

Note: Just ran CarMD scan; it showed green light (no trouble codes found.).

Edited by BSAVictor

Ok, I'm out of ideas other than old school troubleshooting stuff like looking for leaks in vacuum lines and such.

Would you believe we don't own a single ODBII car? The last one was a 2001 POS Windstar and prior to that was a Saturn SL2. We've been NObd for four or five years now.

Thanks, Smacaroni. Will try our new Motor Village (a new "factory dealership"- Chrysler, Dodge, Jeep, Fiat, in Downtown LA). Took a tour of their facility; shop and equipment looks new. We'll see. I still shouldn't need to buy anything by model year 2013, but Fiat/Chrysler has some new midsize, offroad/towing-capable SUVs due to be out by then --so will monitor dealer's/products' performance--maybe 2014 or 2015 would give them chance to work out more "early adopter" bugs?!

It wouldn't hurt to clean the IAC.

Yep, get some carb cleaner and clean that IAC.

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