neko

i have a 90 cherokee ltd cold is starts and idles fine after it gets a lil heat in it it will idle around 1500 to 2000 rpm...could this b the idle air controler?

tjwalker

Yes. I would recommend cleaning it and the throttle body.

The Idle Air Control (IAC) is mounted on the back of the throttle body. The valve controls the idle speed of the engine by controlling the amount of air flowing through the air control passage. It consists of a stepper motor that moves a pintle shaped plunger in and out of the air control passage. When the valve plunger is moved in, the air control passage flows more air which raises the idle speed. When the valve plunger is moved out, the air control passage flows less air which lowers the idle speed. Over time and miles, the IAC can get carboned up which can have an adverse affect on idle quality. Cleaning the IAC may restore proper function and is an easy procedure to perform and good preventive maintenance so it is never a bad idea.

CLEANING THE JEEP 4.0 IDLE AIR CONTROL

Remove the air filter cover, associated hoses and the rubber boot that goes from the air filter cover to the throttle body. Remove the IAC with a torx driver (2 bolts; one can be kind of hard to get to)

“Gently” wiggle out the IAC from the throttle body. Gasket on the IAC can be re-used if it is not damaged

Clean the IAC with a spray can of throttle body cleaner; inexpensive and available at any place that sells auto parts. Throttle body cleaner is recommended rather than carburetor cleaner as it is less harsh, safe for throttle body coatings and is best for this task. Use cleaner, a rag and a toothbrush and or Q-Tips. Be gentle; don’t twist or pull on the pintle that protrudes from the IAC as it is fragile and you could damage it.

Thoroughly spray clean and flush where the IAC seats in the throttle body with the same spray cleaner

It is also a good idea to clean the entire throttle body itself, the butterfly valve inside of the throttle body and all associated linkage as long as you have things disassembled

Reinstall IAC and check idle quality

neko

So I tried took out the iac and cleaned everything...problem is still here..any other ideas wat this might b?

widefieldcherokee

u could have a vaccum leak somewhere check the diagram on the firewall for the vaccum lines for the manifold and see if theyre all goin to the right place thats where i would start

tjwalker

Yes, a vacuum leak is always suspect for a high idle.

But the idle air control is still in play. Cleaning it CAN, but does not GUARANTEE restoration of function.

Get one from a salvage yard for a few bucks and try it if you don't stumble onto the problem.

CherokeeCountry

This thread made my life a lot easier, just started having problems with my idle. Idles around 1500 then drops down to the normal 900 RPMS. Gonna clean the Throttle Body and IAC tomorrow, hope that fixes it.

neko

So I got fed up of messin with it any broke dwn and took it to a mech...turns out it was my screw on my throtle was messed with prior to buying it..hopefully I get a lil better gas milage now...doubt it lol