Mother Nature Fixing My High Idle Issue?

[SmthnD1ff]

Unlikely...

but the seasons change has brought a new symptom to light that may help me narrow down my troubledhooting.

 

BACK STORY

When I got the jeep it had a 2.5 renix w the manual 4 spd, 2WD, and a poor low idle intermittently misding like a plug wasnt firing or lean/rich condition. While driving it home across state lines I found the vacuum line from the throttle body to map disconnected. I reconnected it, had a bite to eat, and started it up and it idled much steadier.

After a few hours on the interstate I pulled over to fill her up and noticed the idle was very high. Got her home and pulled the throttle body, IAC, TPS and cleaned everything, red rtv gasked and reassembled.

I also took this opportunity to check all my vacuum lines and replaced/rerouted a few brittle or improperly run lines using a diagram I found scanned from a FSM.

Idles better but the problem persists.

A few weeks later I picked up a stock air box and new filter to replace the P.O.'s version of a "cold air intake" that consisted of a few platic intake pieces from el cheapo parts store with some sort of faded red rice burner air filter duct taped on the end (no joke)

Quieter but no change.

 

 

 

Possibly unrelated but potentially relevant:

Had a continuity issue between the alt signal and ecu and couldnt find the short so my solution was to buy an external regulator from NAPA for a late 80s Dodge Dakota and bolt it to the inner fender well. Now if you think that sounds like a bandaid- it is, but it fixed the charging issue and my 2 year old Walmart special battery reads 12.3 w eng off and a solid 13.8-14.5 v running.

Also had the exhaust fall out from under the truck when pulling off the interstate one day. The P.O. used exhaust sealant to couple the cat to the header and it had finall had enough of being forced to do a job it was never intended to do. I replaced the section with a cheap thrush muffler from pep boys and some new hangers and scrapped the cat. I didnt notice it when I got it but it never even had a muffler on it, just the cat.

Again, quieter but still screaming.

 

At start up th jeep idles beautifully. Hell half the time I can't tell its runnng for all the insulation I have in the damn thing. After 5-10 minutes at idle or a trip to the shop (4-5 miles) the idles back up there and I'm running the compressor at every stop light for fear the things gonna tear itself apart.

 

End rambling...

 

THE PROBLEM

As soon as th jeep warmed up the idle steadily got higher and higher.

When I turn on the AC compressor the idle drops down. If I start it with the compressor engaged the idle feels lower than it should be until it warms up. When at operating temp engaging the compressor lowers the idle but it still seems a bit higher than I'm comfortable with.

I also noticed the idle decreases ever so slightly when the headlights, stereo, amp and other electronics are engaged simultaneouslt (possibly unrelated but potentially relevant).

The newest symptom is the weather:

THIS JEEP LOVES THE COLD!

Well, what a Florida boy considers cold anyway...

for a few days we had a "cold snap" (30-40°F) and the jeep drove beautifully. No high idle, no need to restrict it with the compressor, just beautiful, flawless purring. Since then our beloved yet bipolar mother nature decided it wasnt quite Christmas yet and temps have bounced back and forth, the problem presenting itself and retreating in turn.

 

Now I bought the jeep in Atlanta, GA, a place where they actually have seasons.

 

Am I just grasping a straws to assume that this is an oxygen sat/density related issue? 32° is not enough to affect the operating temperature (I don't think)

 

I appreciate any input/suggestions and thank you for reading.

 

Kris

[88whitemanche]

I'll be watching this because mine is exactly like yours but the idle is opposite it's running low rpms

[ride172]

My guess would be to check the map sensor. A cold front would lower the air pressure. Also maybe the engine temp sender as it could be telling the computer that it is still cold and needs more fuel.