Help with high Idle at hot/warm start.

I have a 90 xj w/ 4.0l six. When I go to start it when it is warm or hot (when the engine is warm, like when i re-start the car after filling it up with gas, it is cold out side right now.) It starts and revs up to 2800-3000 RPM and stays there. I have only let it run 10-30 sec. at this rpm then shut it off and re start the engine again and it revs up and then drops back down to is normal idle. Some times i have to turn it off and re start it 2-3 times befor it will idle normaly. I have replaced the IAC about 2-3 months ago. The TPS and CPS are 6-7 months old.

Dose any one Know why This happens? or how to fix it?

I was thinking maybe the Intake temp sensor was going bad and telling the computer that the engine is realy cold and to open the IAC valve to open up a little more to let the engine warm up. when in fact the engine is warm so it maks it rev up realy high.

I say this because it seams to only happen when the engine is warm/hot, not first thing in the morning when it is cold.

Thanks for your help,
Curtiss

Sounds like tps or tps connector going bad. Did it on mine like this and new tps and cleaning and tightening the engine side of harness connector fixed it. Good Luck. Greg

Greg,

I replaced the tps 6 months ago. But may be it needs to be adjused. what voltage did you adjust your tps to? or what % of the input volage.

And what did you mean by "cleaning and tightening the engine side of harness connector" how do you clean and tighten your electrical conections?

I just srpay with some electrical contact cleaner then plug and unplug the conector a few times, then put some die-electric grease on the pins. do you do otherwise?

thanks
Curtiss

Also - clean the throttle body :thumbup: