94XJCherokee

97 Cherokee 4.0 aw4

Just recently the jeep started to idle around 1500 rpm.

Anybody have a solution? Thanks guys

tylers89

Take off your idle air control valve and clean it out really well, inside and out. Make sure you put it back on correctly.

tjwalker

The #1 thing I suspect with a high idle is a vacuum leak.

If this were mine, I would start with a comprehensive search for a vacuum leak. Check all vacuum lines and connections. Use a spray can of carb cleaner or even a spray bottle of water. Mist spray all areas where vacuum is present. If vacuum changes where you spray, you know where to concentrate on...........

Good luck and let us know what you find!

94XJCherokee

Thanks guys...I forgot to add, this is only some of the time. And also since the idle problem the jeep sometimes hesitates when its cold in the mornin.

Just replaced tps and map.

Thanks again

94XJCherokee

Bump to top...help me out tjwalker

tjwalker

1. Regardless of whether the high idle is all of the time or some of the time, (does it happen more when cold or hot) you still need to perform that comprehensive check for a vacuum leak. No shortcuts on checking vacuum for a root cause here.

2. I'd consider a thorough cleaning of BOTH the throttle body and idle air control. Best to remove the throttle body if it's nasty, but here is information for a cleaning while still installed.
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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

94XJCherokee

It only does it when its cold. So that's y I'm leaning more toward iac.

I will be checking for vacum leaks this weekend. Thanks tj

ZINGGG

Take off the throttle body and clean the crap out of it with throttle body cleaner. Make it sparkle it's so clean. Then disconnect the idle air control valve and spray it with carb cleaner and scrub it with an old toothbrush. Hook everything back up with a new throttle body gasket and torque it down.

This is in addition to looking for a vacuum leak, as suggested already

94XJCherokee

Thanks, I will be doing that this wkend along with a tune up. Thanks again evrybdy

peep

My brother in laws tooth brush always volunteers for carb cleaning duty.