96Xj-A-SKWAD

96 xj stock motor ( PO says it was a replacement from jeep IDK bout that)



RECENT WORK DONE

-recently dropped fuel tank to weld some of the unibody frame

-Installed new exhaust from after down pipe & back ( Thunderbolt cat, new Rear 02 sensor, new muffler and tail pipe)

-recently changed oil

-Fuel filter about a year ago

-Air filter clean

-lucas oil -injector cleaner every three months

-No apparent Vac leaks

-Duty Purge sometimes clicks



Issues/SYMPTOMS



ok so here it goes, Jeep runs like a top, flawless. that is until I took a hour long ride (@ avg 45-65 MPH). A trip I frequently did over the summer. On the way home I stopped to take a leak on the side of the parkway and noticed I was idling funny. almost seemed like she wanted to stall out. Also noticed a very unfamiliar smell coming from the jeep hard to describe. (I assumed running lean ) at stop signs it would really grumble hard. In Park at idle was worse than driving.



CEL came on about 10 min later while driving. Code 12 ( battery Disconnect) and code 51 (Oxygen sensor stuck at lean position)

Soo I searched the magical interwebs and found a few possible fixes.



I went out and bout a 85$ MAP sensor. Cleared the CEL and replaced the old MAP. Started her up CEL was gone and she ran great for about 3 days. drove locally.



Today I went on the same hour long trip to pick up a boat trailer. Just as I got to the marina she started idling funny again. started home and the CEL came on again. Same codes (both times this happened was at the same long trip)



I think my MPG went down too.



Stopped at a buddys house (whose 2000 xj has the same or similar issue) and I reset the computer again. I was good for about 15 min of driving at an AVG of 45 MPH



Before I start replacing the TPS, forward o2 sensor, injectors, IAC, ETC.,

Does anyone have any suggestion.



Fuel pump, Vac leak , ? idk where to start.



Thanks all in advance

-Pete

EZEARL

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