High Idling?

[Jeep]

Why does my '92 4.0 Auto idle so high at start up. It doesn't matter if the engine or weather is hot, cold or in between :helpme:

Thanks

 

[ZmOz]

Take off the throttle body, remove all the sensors, and clean the hell out of it. Also clean the IAC. You may need a new TPS...

 

[XJade]

There's tons of useful info about this problem in the archives. Do a search on "high idle", "TPS" ("Throttle Position Sensor"), "throttle", etc...You'll harvest something that may be of help to you. Good luck.

 

[Dr. Dyno]

It's most likely that your IAC motor has stuck because of dirt accumulation. Simply disconnect the negative battery terminal, remove the TB, remove the IAC motor from the TB, clean both TB and IAC thoroughly, put everything back, reconnect the battery, and fire up the engine.

 

[jneary]

tps is can be the problem. if you have a scan tool it should read 0% it idle, if not it is probably bad

 

[Dr. Dyno]

A bad TPS usually causes an erratic idle rather than a steady high idle. It'll also cause the engine to intermittently buck and hesitate when you change throttle position while you're driving.

 

[Jeep]

Alright, I'm going to have to play dumb here :confused1 . But what is an IAC Motor?

Thanks for the help

 

[XJade]

Idle Air Control aka idle control unit, etc.

it's on the throttle body next to the Throttle Position Sensor.

 

[Jeep]

Yea, this happens just at start up and last only a couple of seconds. I'll check these out. Thanks for the info :wave:

 

[jneary]

the other day i had a 93 with the tps reading 3% at idle, changed it and it idled fine at 0% like it is supposed to be. the tps can work fine off idle and can still be bad. i would suggest hooking up a scan tool to see the reading at idle