whargoul

My wife has a 1999 Jeep Cherokee Sport 4.0L Automatic, it was a gift from her father.
It has about 133k miles on it.
Back in December I started having problems with it wanting to start.
After many failed guess and my son getting dirty, we figured out it was a head gasket leak that had gotten into the starter itself..

Sprayed a health dose of Berrymans B-33 and I took it to the car wash to clean the most of the oil off.

It starts like brand new, however I now have a new problem.

When you 1st start the jeep it typically idles @ 800ish. Now usually when the engine starts to warm up, when it drops to low RPM it dies, however if I shift into neutral it doesn't die( RPMs are higher).

Any ideas on what I messed up on?
I've been thinking it might be a Idle Air Control but I really have no idea honestly..

I'm not really known for my mechanical skill or knowledge but I love learning and fixing things myself..


Thanks for reading.

wiggles

If you suspect the iac than while its running unplug it and if it doesn't change than bingo

whargoul

Unplugged the IAC and it ran like a dream again..

big thank you to this site, without it I would have been out more hair and a ton of cash..

The "shade tree" mechanic I had helping me thought it was the fuel filter..

cruiser54

Try this. It's considered normal maintenance:


Courtesy of TJWalker:

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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