Hi everyone, thanks for checking out my first post for help!

My Jeep is starting at about 800 rpms and gradually rising to about 1000 as it gets up toward 210. It'll just sit there at 1000 then. Shifting into any gear brings it down to around 600ish. Turning on the A/C or defrost option will bring down the rpms when in Park. I've had the truck for about 6 months and the electric fan has always kicked on and off constantly with A/C or defrost on. Like, on for 5 seconds, then off, then on again for a few seconds, etc. When in Park and with the A/C or defrost on, I can watch the RPMs rise and fall when the fan kicks on and off.

It is not overheating... yet. It does creep up just a bit past 210 on the gauge. There are no codes, no CEL. I recently cleaned the throttle body and did a new gasket.

OTHER CONSIDERATIONS: The truck was stolen recently. The bracket that holds the ignition lock cylinder was smashed into non-existence and I had to replace the whole steering column. I drove it for about two weeks with the broken column by just lining up the ignition cylinder and turning to start (key and cylinder were NOT in the column as I drove.) The ignition was probably not always "turned" to the correct position as I was driving.

The high idle began during this time.

Last weekend I did the ignition key sequence for resetting the computer. It barely started after that and I had to give it gas to keep it going. Since that one terrible start though, it's been better almost every time. Cranks quickly and the idle isn't rough really, just very gradually climbs.

One last thing: radiator cap went about a week ago. Got to work and saw fluid in my fender well, checked under hood and saw it leaking out of the cap. Rubber gasket was toast. New standard cap seems fine so far. THEN two days ago, lifted hood and saw small amount of fluid on top of thermostat housing. Looked like it was dripped from the right mounted hose on top there.

OK, well that's a bunch of random stuff to put out there, haha. Anybody have thoughts?

 

If it's done that high idle since you've had it, it's possible the PO installed an Extended Idle Switch function that raises the idle to 1000 only when in Park or Neutral. Look at the PCM and it's A plug. That's the one closest to the firewall. See if the grey wire coming out of the plug, Cavity 12, has a spliced in wire going somewhere. If it does, cut that wire, the spliced in one, far enough away so you can put it back together if that doesn't do anything.

There is a built in function for Police use that raises the idle to 1000 to keep the alternator charging to supply the radios they use if they are going to be idling for a while. All you need to do to use that function is to ground the grey wire coming out of plug A, cavity 12, thru a switch. The PO may have installed a switch somewhere that's not obvious and you may have tripped it somehow. In the Police version, there are 4 switches on the center console and one will say "Extended Idle."

 

My first guess would be a vacuum leak or idle air control (IAC) going bad. I'd start by looking over all the hose and vacuum lines and clean the throttle body.