i have a 1990 jeep cherokee 4.0l m/t. my idle goes up around 1200-1800.
i have replaced my idle air control and my throttle pos sensor. i've checked idle air control and it's working. any sugestions or is this another jeep mystery?

 

uhm wasnt there this exact same thread a page back?

read the info there...

https://www.cherokeeforum.com/f2/high-idle-69360/

 

I jsut had this problem bud. It was my ECT not clipping in all the way. Replaced the clip, and now I'm good to go. Do you have a loss of coolant temp on the dash gauge?

 

Vacuum leak is an extremely common cause of high idle. I would perform a "comprehensive" search for a vacuum leak if I were you...

 

I have a high idle and low temp reading whats the relationship?

 

Clean your throttle body. I cleaned mine and my problems went away. I did a write up on how to replace the IAC motor but then all you need to do is take out the 3 bolts holding the throttly body in there and a hose then your ready to clean.

https://www.cherokeeforum.com/f52/di...acement-66578/

 

i did a complete vacume house replace about 6 months ago it did not fix it, but who is to say that one peace was not missing and did not get replaced. guess i will try to clean up my TB and go from there. and my jeep only has the idiot lights. lol. so i cant check the temp change unless i put in my own.

 

Does your XJ get up to operating temp, or does it not read at all?

 

it stays around the 1/4 mark 155 or so and if i let it idle for a little it will get up to around 210 but never when im driving

 

Job #1 for you is to get your coolant temperature to CONSISTENTLY stay in the 200-210 range.

Your engine won't run right until you achieve this.

I would install a new Jeep or Stant SuperStat 195 degree thermostat. That might fix your coolant temp issue.

 

I have high idle in Park/Neutral and low coolant temp...What is the ECT?

 

Did you adjust the new TPS?

 

I had a high idle running at 1500, with low temperature. I read all the threads and started researching parts pricing mentioned in this and other threads. I instead put 5-6 ounces of Seafoam in my crankcase, and 27 ounces in a full tank of gas. Insanely, in less than a half tank burned through the high idle issue disappeared. In fact, the Jeep seems to be running better than ever! Try Seafoam before you spend money on parts that may, or may not work. Good luck.