I have replaced the CPS and the TPS yet my 93 JGCL 4.0 still has rough idle. It is not as bad or as frequent as it was but it is still there. This is driving me crazy. The engine runs great at all other rpm ranges. It seems to only happen when I am at a stop at a red light, etc... Any help would be more than appreciated.

Try your fuel regulator, they go bad, and check to see if you cap and rotor have built up in the inside, I replaced mine with brass poasts in the cap, it's a world or differance.

Check the IAC Motor on the back of the Throttle Body. Try cleaning both the IAC and the Throttle Body with Carb Cleaner and a tooth brush. The IAC is known for failure on Jeeps. Also check for any vacuum leaks and wire arcing. Make sure your Altenator is working right at Idle should be around 13-15 volts.

I did pull the distributor cap and rotor. The post are worn considerably and will replace both of those today. I guess after 225K miles I would be worn too. Where is the fuel regulator located?

Check the IAC Motor on the back of the Throttle Body. Try cleaning both the IAC and the Throttle Body with Carb Cleaner and a tooth brush. The IAC is known for failure on Jeeps. Also check for any vacuum leaks and wire arcing. Make sure your Altenator is working right at Idle should be around 13-15 volts.

I had previously cleaned the throttle body a couple weeks ago but I am not sure about the IAC motor. Is it attached to the throttle body? What does it do? Thanks

I did pull the distributor cap and rotor. The post are worn considerably and will replace both of those today. I guess after 225K miles I would be worn too. Where is the fuel regulator located?

I also found my PCV is stuck closed so that will be replaced too. Will check alternator voltage and for vacuum leaks.

The IAC is on the back of the Throttle Body it has 2 Torker T20 I think that holds it on.

Trust me and get the brass contacts/poast cap and rotor, it will not corrode like the Alum.

The poasts dont really "ware away" they corrode.

I have seen Alum contacts corrode in 2 months!!! I even used WD-40 in the cap, it's worth the extra few bucks, and piece of mind that it's not going to fail.

Also as a side note, make sure the rubber around the PCV is good, I had to replace mine because it leaked after I removed the old PCV.

Good luck, hope this helped/s

Trust me and get the brass contacts/poast cap and rotor, it will not corrode like the Alum.

The poasts dont really "ware away" they corrode.

I have seen Alum contacts corrode in 2 months!!! I even used WD-40 in the cap, it's worth the extra few bucks, and piece of mind that it's not going to fail.

Also as a side note, make sure the rubber around the PCV is good, I had to replace mine because it leaked after I removed the old PCV.

Good luck, hope this helped/s


I replaced the distributor cap and rotor with the brass post type last Friday. The difference in the way engine runs is like night and day. Almost all roughness has gone. I should have replaced them a long time ago. PCV is now good to go also. There is still a very rare slight roughness in the idle and sometimes when I start accelerating. I will try cleaning the IAC motor and throttle body as was suggested by another poster. I am getting there. My Jeep is running better now than it has for quite some time. Thanks

The IAC is on the back of the Throttle Body it has 2 Torker T20 I think that holds it on.

Thanks, I will remove it and clean it. Exactly what does IAC stand for and what does it do?

I'm glad I could give my 2 Cents.
I hope that you can pass it on to somebody some day!