Ok so I have noticed this problem ever since owning my XJ. The truck can be sitting there in park and if I turn on the A/C or even the heat it will idle high then low then high and low it's really weird however I can even notice it when I am driving down the highway for some reason. I guess I am just trying to figure out is this normal? Has anyone else ever noticed this problem with there XJ? Thanks in advance for all the help also where can I purchase one of those cherokeeforum.com stickers for my jeep?

 

When you turn on your a/c, the idle is going to go up a little. It's the ECU bringing the idle up, becaus theres another load put on the engine. When the a/c clutch disengages, the ecu says no load and brings the idle back down. As far as driving, the a/c clutch will engage and disengage as the pressures in the system change. As far as your heat is concerned, does it happen when you have the defroster on? Because, when you turn on your defroster, the a/c compressor turns on. This is to keep the oil in the system circulating, so come that really hot day in summer you don't hit the a/c switch and find theres no oil in the bearings in the compressor and burn them out, the first time you use it. They do this because .... who turns their a/c on in the winter?....Hope this is what you mean.....

 

Oh, and by the way, if its really hot out and your compressor is on/off/on/off/on/off, I would check the charge. It may be low....its the low pressure cut-off shutting it off...

 

Thanks for your help but what I mean't is that is it normal for it to just be sitting there in park and I turn the A/C or heater on for that matter and the idle will go up and down up and down up and down? I will take a video later and post it on here and let you guys listen to it for yourself but something doesn't seem right. However I am new to jeeps so maybe its a jeep thing.

 

That don't happen to just jeeps, its all cars.....and yes its normal....