yea the idle is up and down and never constant. but this problem is only about 70% of the time sometimes it just goes away.

 

I went on a trail run with a guy not that long ago who took a water crossing way too fast and his jeep started running really erratically. It would be fine then it would stall then it would idle rough so we limped it to the trail head. At the trail head while we were airing back up we decided to take one last look under the hood and near the intake there is a wire harness going to a sensor in the air tube just before the throttle body. We took that connector off and blew it out and then it ran normal.

I know you probably don't have water in anything but it had similar symptoms just greatly amplified. I wonder if that sensor and or plug could be the problem. I assume it is some kind of air flow sensor. Maybe it needs to be cleaned or the contacts in the connector need to be cleaned. It might be worth a try.

I am not a mechanic but I would just use electrical contact cleaner from an auto parts store on the connector but as for the sensor I am not sure. You have to be careful not to damage them they can be very sensitive.

When the truck I had before my JK was running a rough I cleaned the Mass Air Flow Sensor with some electrical contact cleaner and it took care of the problem. I don't know if that will hurt this sensor or not.

Anyone else know how to clean this sensor?

 

Kind of a longshot, but are you using a thicker oil than 5W-30? That could account for a fluctuating idle as well.

 

Yes thats the mass air flo sensor and you may be onto something i will check the connections for water or mud particles

 

nope i use Mobil 1 synthetic 5W20

 

Don't just check the connectors check the sensor too. It could be dirty if you do a lot of wheeling. Some of that dust eventually gets around the best of the air filters.

 

its spotless i clean out my filter every time i change my oil and check the sensor and the intake toob

 

Oh well it was worth a try. Good luck trying to figure it out, if I think of something else I will post it hear. Let me know if you find the problem.

 

I just thought all Jeeps did that. I had an 04 that did it and now have an 08 and it does it sometimes as well. That's actually part of the reason I traded in my 04, the dealership told me, "Yes, it idles rough but only when you first start it and we can't figure out why. Sorry, you'll just have to come get it." So I traded for my 08.

 

My 92 YJ never did it but my 05 Grand Cherokee did.