Sep 21, 2015, 03:49 PM
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XJ Ask the Question Thread
CF Veteran
Joined: Jul 2013
Posts: 1,154
Likes: 40
Year: 2000
Model: Cherokee (XJ)
Engine: 4.0
ill put it to the test tomorrow. nice little cruise then start it up after 15 minutes
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,578
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
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
Herp Derp Jerp
Joined: Nov 2011
Posts: 18,251
Likes: 17
From: Parham, ON
Year: 1999
Model: Cherokee
Engine: 4.0L OBD-II
Went to start it up after it being turned off for about 10 minutes (unloading groceries after trip) and it started idling VERY rough. Almost bouncing i could say lol definitely coming from the front end. not a lot of response when i gave it some gas, but after i started moving a good bit everything was fine. Drove it to jimmy johns and there were no other problems. Ill be checking it tomorrow morning to see if the problem persists.
Any ideas? No CEL, engine not overheated, oil pressure gauge at 80 (like it always is). thought i smelled something burning but it was only for a few seconds then the smell went away.
Thank you for any input!
EDIT: 2000 sport with 125,500 miles
Any ideas? No CEL, engine not overheated, oil pressure gauge at 80 (like it always is). thought i smelled something burning but it was only for a few seconds then the smell went away.
Thank you for any input!
EDIT: 2000 sport with 125,500 miles
Also your oil pressure is likely a bad sending unit or wiring. It shows 80 before you even start the engine, right?
CF Veteran
Joined: Jul 2013
Posts: 1,154
Likes: 40
Year: 2000
Model: Cherokee (XJ)
Engine: 4.0
CF Veteran
Joined: Oct 2012
Posts: 2,314
Likes: 3
From: Canton, GA
Year: 1996
Model: Cherokee
Engine: 4.0
I'm not sure where it's coming from, exactly... but yes, I look back while I'm braking and see thin white smoke coming from the Jeep. I just assumed that my brand new rotors/pads wouldn't be giving me an issue.
CF Veteran
Joined: Aug 2012
Posts: 1,539
Likes: 0
From: ks
Year: 1998
Model: Cherokee
Engine: 4.0
Sounds odd, id jack up the rear and spin the wheels to see if they are catching. If it were exhaust you would have noticed it by now... pretty weird, i've never had this issue.
CF Veteran
Joined: Aug 2009
Posts: 5,676
Likes: 301
From: WV
Year: '96
Model: Cherokee
CF Veteran
Joined: Oct 2012
Posts: 2,314
Likes: 3
From: Canton, GA
Year: 1996
Model: Cherokee
Engine: 4.0
However, I do have something going on with my cat (I think?).
My check engine like will go on and off for code p420. It'll come on, I'll drive a couple hundred miles, it'll go away for like months. Then come back one day. Then go away again.