I've got an 2.5l 86 that will not come down from 3000 rpm. It had this problem before i cleaned the TB and replaced the TPS but that only brought it back down to 1500 and at times would go back to normal.

I DO NOT have an IAC so that's easy to rule out. I don't have a vacuum leak and everything is getting enough power. I've been all over the internet so i know the usual suspects.

The last thing i can think of is the MAP, that's the last on the list because the PO replaced it when i bought it back in February. And a way out idea may be a shorted cruise control.... I'm really just grasping for straws at this point.

Any ideas are greatly appreciated. I'm new to Jeeps, i was a Suburban guy before, so please be gentle haha. Thanks.

 

Remove your vacuum connections from the intake one by one and block the intake fitting.
If your idle comes back down, investigate whatever that line feeds. You might not have a line leaking, but one of the vacuum operated devices might be.
No intake leaks? Bolts tight?
Where did your IAC go? I see one listed for your year 2.5

 

Yea, my 84 2.5 has an IAC....It's raining, so I ain't gonna go out and double check....

 

Great idea, I'll do that today while i'm waiting for my MAP to arrive. There aren't any intake leaks and i checked all my bolt last night. I'll double check today while i've got the time. Hahaha good question. For some reason this model TB doesn't have one, i have a Idle Speed Actuator instead.

I thought the ISA was the problem last time since the connector for it was shot. I replaced it then (about two months ago) and it helped the issue. But after watching it the ISA for movement last night i noticed it wasn't the problem. It didn't move but the idle was jumping from 2200 to 3000 without the throttle being moved. So i'm assuming that fuel is being dumped in the TB.

Days like today make me miss my carbureted 72 C10....

 

Was just remembering...my 84 is carbonated, but still has some sort of IAC deal there...IIRC.

 

with my experience on the 2.5 check the Intake gasket. My friend's wouldn't run right to save its life, spayed some carb cleaner where the intake meets the head and bam it was sucking in air.

 

Well here's an update. So yesterday i took the day off of work and spent all day and i mean all day working on my jeep, from 8am to midnight. I did everything i could think of, i even removed the intake manifold and made sure it was seated properly... and nothing! I checked gaskets, vacuum lines, grounds, sensors, fuel injector, wiring and still no clear sign why it was idling so damn high.

This morning i decided i'd drive it a while to make sure it did just need to run for a while to "reset" it's self. While i was driving around scratching my head i purposely stalled and guess what! The damn thing dropped down to 1,100 rpm after i started it back up and has stayed there all day, so far. As a matter of fact it runs better than it has since i bought it back in February.

Go figure, i'd spend all that time and money trying to fix it yesterday and all i had to do was stall. I still have no clue what so ever why it was acting the way it was.