austinjoe13

1990 4.0 likes to idle around 1200 rpm when warmed up. I can start it and let it run for a bit and it's fine, 800 or so. After I get on the road it bumps up and fights the brakes. I readjusted the TPS a couple nights ago and it helped, but it's back now. Any ideas?

RTorrez1

Have you check for vacuum leaks? A vacuum leak will also cause high idle. Just something to look at.

freegdr

Check intake/exhaust manifold bolts very common occurance they loosen up and cause vacuum leak....

cruiser54

Leaning towards vacuum leak.

Did you adjust the TPS on the "engine" side? The flat connector? 17% ring a bell?

austinjoe13

I did find a loose bolt. Finger loose! And Yes, engine side of the sensor. It was set pretty low before.

cruiser54

Good. Have you found any vacuum leaks using the throttle body cleaner?

austinjoe13

I have not tried because I am making the christmas rounds. I will be able to tear into it better this week and get every bolt.

austinjoe13

I noticed today that when I let my jeep warm up a little bit it leaves soot spots under and behind the tip. But it's getting great mileage... I started it up this morning and it started chugging like the map was reading atmospheric pressure.

cruiser54

Watery soot is normal.

How's the vacuum line from your throttle body to MAP sensor?

austinjoe13

Just fine. I shut it off right away and wiggled the ends of it and it sounded alright.

austinjoe13

It's cured! There were some really loose bolts under the manifold

cruiser54

freegdr nailed it in post 3!!!

Cool **** austinjoe13!!

austinjoe13

There were two that I could wiggle the washers on. Like I said, really loose lol

cruiser54

Extremely common problem.

Any of you guys out there who haven't checked your intake manifold bolts for tightness, DO IT!