cleenrob

what problems would be associated with a bad IAC?

Roler

As the name states, its involved in regulating the air inflow during idle, or whenever your foot comes of the gas, like slowing down a hill or come to a stop. The device is quite simple, a rod or pinion its called, moves in and out, whenever ur engine goes idle. Symptoms related to this usually rekate to the pinion being stuck, not allowing the required or desired amount of air in, resulting in rough idle, dying after stating up, stalling whilst sit in front of traffic lights etc. Surging ,high,or low idle is another one, where to ECU is getting incorrect information and tries to adjust the air/fuel mix.
Cleaning the IAC is therefore an item on the list when you have symptoms like that, its simple and there is info available on theforum how to do this. Hope this helps.

cruiser54

Ever done this? If not, it's about time.

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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

cleenrob

Yea i took the throlt body off and gave it a really good cleaning and im stuck with a high idle at about 1200 rpm and im thinking that may be my problem cause i cant find any vacum leaks anywhere

cruiser54

Did you remove and clean the IAC?

zombie jeep101

Here's what mine looked like, cleaned it, still have problems ???

cruiser54

Still having problems? What kind?

cleenrob

yes i did
and she still idles high and sputters now and then and does this weird surging thing on the highway where the rpms jump around like craze in a 300 rpm range
Ive got a stung feeling that the IAC is going nuts

cruiser54

TPS could be taking a dump on you.

cleenrob

I replaced the tps with no improvement.

zombie jeep101

High idle, weird shifting, violent shaking when acceleration and then letting off the gas

cruiser54

Have you sprayed for vacuum leaks using throttle body cleaner?

cruiser54

How about your TPS? Ever test it?

zombie jeep101

Never have. Not sure how to?

VTJeep

http://www.jeepforum.com/forum/f11/how-test-tps-610386/post #5