So i just bought an 89 xj. my second jeep. and i'm having problems. it idles super high.. almost 2,000 rpm. i read in an article that with my renix engine, the bolts that hold the intake and exhaust on can work loose, and run high idle. well... tightened them all. they were loose. but still a high idle. any suggestions?

 

Welcome to the Cherokee Forum

Check for other vacuum leaks and if you haven't already torque all the intake/exhaust bolts to proper specs and in the proper sequence.

I'd be looking at your TPS. It could be bad or out of adjustment. Do a search for the adjustment and testing procedures, its a common problems on RENIX motors. Theres a bunch of threads and writeups about this along with high idle problems, read through those. Google is your best friend and will answer most questions, if your stumped, we're glad to help you out.

 

thanks yeah i started looking at the throttle but hadn't gotten into anything yet. what vacuum line should i look at first?

 

all lines looking for broken un plugged cracked

 

Job #1 is to perform a comprehensive search for a vacuum leak, as high idle is often related to that. Use some carb cleaner or a spray bottle misting water and spray around everything vacuum related. If the idle changes while you are spraying, you know what to suspect.

Idle air control is also in play here. Here is more.

----------------------------------------------

The Idle Air Control (IAC) is mounted on the back of the throttle body. 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