niktheknife

im idling at about 1000 in drive but if i put it in nuetral or park it goes up to about 1200-1500, ive been lookin for a vacuum leak for awhile now. any other suggestions?

another prob, my engine(4.0 4x4 auto) runs past 210degrees alot lately and i think its because i have a stuck thermostat or something idk. there is some kinda gunk in my coolant resevoir so should i flush it all out?

fantic238

Replace the IAC idle stepper motor on the throttle body.

sgtskid

x2 mine did the same thing

xj4fun

Question - Does it alway idle high?

By this I mean if it's cold or just started does it still idle the same as when it at operating temps?

Kent

91XJMudMan

x3 on the IAC valve. My jeep did the same thing until I pocketed one from the junkyard and fixed it. And mine use to overheated all the time. I noticed I had a water leak from the water pump, a lot of gunk in my radiator and motor, and a slightly blown head gasket. So... a new water pump, a flushed out radiator and motor, and tightening the cylinder head down a bit I was good. I also swapped out the stock 180 thermostat for a 160. Hope this helps

niktheknife

when started it wont idle high, but after the temp gets up abit it picks up, and its only in Park and Neutral, none of the other gears. so i should look for a new IAC? i cant clean the one i already have?

91XJMudMan

I'm not sure if you can clean it, but I do know its small enough to fit in a pocket and that makes it really easy to get one from the junkyard lol

xj4fun

My bet is an intake/exhaust manifold leak. Reason being it idles find cold. Additionally when in gear there is torque applied that brings down the idle.

Here's a link where I posted a fairly extensive document I wrote on idle issues years ago.

https://www.cherokeeforum.com/f2/high...99/#post389882

Hope this helps,
Kent

ahenderl

I went through the exact same thing a few months ago and it was the TPS sensor.

First, I cleaned the IAC. The problem was still there so I replaced the IAC. Still had the problem. I replaced the TPS and problem went away for a couple of weeks. The high idle returned, so I started chasing vacuum leaks and such. I thought it couldn't be the TPS sensor b/c it was new. I finally got an intermettent CE light, so I picked up an OBD2 scanner. It turns out that the TPS had a 80% reading at idle. I reluctantly coughed up $60 for another TPS and no more problem. It has been good for at least 8-10 weeks.

If you get a new TPS, buy a good one. My bargain basement sensor caused me a lot of headaches.

If this helps, my symptoms were the following:

It would start and idle as normal.
It would idle properly when in gear (mine is an auto).
When shifted to park or neutral at a stop light, it would idle up to 1500.
If I shut it off and started it back up immediately, it would idle normally.

I only noticed it because when I shifted to park when I got home or to work, it would idle up to 1500.

If you have a vacuum leak, it should not return to a normal idle if you shut it off and fire it right back up. Usually, if it leaks, it will leak all the time. My problem was intermittent.