4.0 idling high

[MichaelT]

The jeep is a 99 TJ with 4.0. It's idling at about 1250 rpm. It does it almost all the time, not just when its warming up. Any ideas of what might be causing this? Thanks -Mike

 

[gt500swim]

vaccum leak

 

[willness33]

vaccum leak

That or a dirty IAC or a combination of both.

 

[Jeffrey92r]

It's you throttle position sensor I'm 95% sure

 

[VortecJeep]

Idle Air Control valve would be my first thought.

 

[tsouther]

X2 on the throttle position sensor. Had the same problem with my 98 tj two weeks ago.

 

[jeepparts]

I would IAC motor wife 04 TJ had a similar problem, so i pulled the throttle body and cleaned the tb and the iac motor now runs like a champ.

 

[willness33]

Dirty IAC. Oh wait, I already said that. Get a can of carb cleaner, take it off, clean it and in the intake where it goes. Prove me wrong. I dare ya. Then if I am wrong, start looking for a vacuum leak or a leak in the intake somewhere.

A TPS problem is far more uncommon than my previous mentioned issues. A TPS is super easy to rule out with an analog volt meter.

 

[gt500swim]

haha i was just about to say why not just pull the tbody off and soak it hahah.

 

[bannerp]

Clean your TB and go to your local shop and have them clear all the adaptive memory. Also spray carb cleaner around the base of the TB and around all the vacuum hoses if the engine idles up you have a leak clean the IAC valve as well just for good measure.