cashmoney11

1991 jeep cherokee 4.0 laredo high output.

Hello everyone my jeep has in issue... when i start her up when she is cold she starts up good then the rpms drop and about 25% of the time she will die. and while it is doing this i cant gain rpms by giving it more throttle or anything. but once it is warm it runs perfectly fine. it seems like it is starting to do it more often. like were it is warmer and warmer. cuse it just use to do it everymorning but now it happens sometimes during the day.

i would like to thank everyone in advance.

cashmoney11

bump

VTJeep

Could be a couple of things- the o2's are possible. Is CEL on? If not you can still get one on there to see if anything is stored in there.

tjwalker

1. Test the coolant temp sensor. If it is providing bogus input to the computer, it can create funky symptoms when cold.

2. Be sure tuneup hardware is fresh. Never underestimate the importance of the secondary ignition system! Fresh Champion copper plugs gapped to .035, new quality plug wires, distributor cap and rotor. And toss in a fuel filter while you're at it.

3. Clean both the throttle body AND the idle air control. Both can contribute to idle issues. More on that below.

Good luck and let us know what you find!


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

cashmoney11

kk i will do all of that tomorrow and see how she runs! thanks ill keep you posted!

cashmoney11

She still just low ideals then dies. I was thinking fuel pump maybe.. but other then that I'm stumped.

tjwalker

Still, after trying what?

Fuel pump is generally not involved in a low idle.

cashmoney11

Tune up new rotor dist cap and wires new fuel filter. And this smorning I started her up she ran for about 1 minute then rpms dropped to 100 then started making a clunking noise then the rpms jumped to 2000 and she ran fine after that. O and I cleaned the Iac.. but I'm not sure how "gently" I cleaned it.. but my jeep idels fine. Thanks again for your help.

cashmoney11

It seems like she is dying more and more when its colder.. thanks again!

cashmoney11

Bump.

cashmoney11

Bump again.

cashmoney11

Bump again..

cashmoney11

Bump.

cashmoney11

Do you guys think maybe it could be the cps..? When I start it up and throw it in drive in about 10 seconds it ideals down and misfires. Thanks again.