Hey y'all!

I just gone done doing quite a bit of work to my 97 Cherokee 4.0L w/AW4 over the past few weeks and i am having some slight issues... Now, i have been doing some research on here this morning but have yet to come up with something that describes my issue exactly.

So, i have done a new APN header, rear mail seal, new gaskets top to bottom, full tune-up and cut the old cat/muffler off in preperation for the new ones.

The issue that i am having is a slightly high idle (about 800-900rpm) and when i hit the gas for just a quick rev or while driving, the engine will stay at about 1200-1350 rpm all by itself for a few seconds before idleing back down...

Could this just be a vacuum leak? Am i over thinking this? Where would be a good starting point as i have not check for vacuum leaks as of yet...

 

Vacuum line or IAC?

 

I planned on cleaning my IAC when i got off today and see if that helps...

I dont think i have ever seen a vehicle do this... Any other ideas?

 

My 88 would do that if it was in park or N..if you hit the gas it would stay idled up till you put it in gear. Pulled the IAC...cleaned it with some carb cleaner reinstalled..fixed!

 

Like XJ88 said, I would start with the IAC

 

I thought that it was only doing it in park or neutral, but it turns out even when it is in gear and and on the trail it does the same thing... makes using 4LO pretty scary at times! LOL

 

Id still start with the IAC..maybe seafoam the Tb while your under the hood. Its a start.

 

I seafoamed the tank about 2 weekes ago... No significant difference...

 

The gas tank? Did you dump some down the TB? Thats when i noticed a difference.

 

Start here.....Good luck!
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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

 

Thanks TJ! I had already found another thread that you had posted this on and printed it out along with the TPS sensor portion as well.

Thanks for the help gentlemen! Ill let y'all know how it goes...

 

You need to come down and wheel again! I didnt make it last time..

Brian is working on his new project.
I just picked up an 00 xj with like 90k on it..so itll be under the knife soon.

 

I am leaving for WITC on Saturday morning for 4 days and then mine is going back under the knife for 35's, axles, cage, and what not... I'd love to come back down there though A.S.A.P!!!!!!!

 

I hear ya.. I have death wobble like no other in the new rig.. Gotta get it sorted out but with recent holidays..and moving into a new house..having a 6 month old.. I have very few monies! haha