Why does my Jeep Idle at 2,500 every other start?

[Joshooha]

NO. The T-stat air control only moves the air source to the air filter, it has absolutely nothing to with engine idle! I can only change the incoming air source, from a cold source to a hot source. The IAC and TPS are the only two sensors that truly control Idle speed. A change in inlet air temp can affect idle speed if the IAT (MAT) is giving out bad data, but it would be repeatable, like only show up for hot, or cold starts.

Awesome, thanks for the clarification!

 

[Shorty]

I've read all the above posts but don't see the thing that finally cured my idle issues with my 90. I have a few vacuum leaks and once they were fixed no more fast idle issues. Coincidence..................I think not!!!

It wouldn't hurt to plug off the vacuum lines to the air control diaphragm and try starting it, however. If the diaphragm were torn or deteriorated, you could create an unregulated vacuum leak that the IAC cannot compensate for effectively-- just a thought.....

I think I saw that suggested somewhere in there......