My 2000 cherokee has developed a problem with the idle. It began like this:

Idle was very high, like 2K rpm.. I found a vacuum line had come off at manifold so I repaired the hose and re-attached it. Then it Idled fine for a while.

Then all at once it began idling so low that it would die. Run good as long as I kept the peddle down and off-idle. But when I let off it would idle down and die..
So I took breather off etc and sprayed everything clean including the IAC motor and the IAC slot in the throttle body...OK now it idled High again, Not as high as before but too high..I left it that way for maybe two weeks. Now it started idling super low again and dies everytime I let off the peddle...

What might be going on here, It does give me an IAC code that says IAC circuit problem. But could be several things listed..

What is common to fail on these things The IAC motor itself ?? Thats 70.00 to find out...

Any ideas???

 

i will check this thread from my phone app so it may look different idk ??

Can the IAC motor be tested ?

 

try cleaning the throttle body and IAC. You need a 10mm socket and a torx socket, but I can't remember what size

 

Try cleaning it first. If that doesn't resolve and you still set a code for it, replace it.
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The Idle Air Control (IAC) is mounted on the back of the throttle body. (front for 87-90) 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

 

Test your throttle position sensor