High idle

kc7bur · May 7, 2004

Hello everybody.
I've got an '89 4.0. When it's cold it idles at 1000 in Park. However, after its been running it idles up to 1500 in park. I hav'nt found any obvious vacuum leaks. It has a new O2 sensor. Could it be some other sensor?
It has 183,000 miles. New alternator, battery, 3-core GDI radiator, starter, brakes, etc....

89xj · May 7, 2004

could be dirty IAC.

could be TPS, which you can test with a mutlimeter.

could be loose intake/exhaust bolts.

kc7bur · May 7, 2004

I was thinking its time to replace the TPS anyways, just so I know its new.
UH, IAC?
I will check bolts. I replaced the muffler/ cat a couple years ago.

What a acceptable reading for the multimeter and where/ how do I test it?

Thanks, Jay.

RINGKONG · May 7, 2004

kc7bur said:
I was thinking its time to replace the TPS anyways, just so I know its new.
UH, IAC?
I will check bolts. I replaced the muffler/ cat a couple years ago.

What a acceptable reading for the multimeter and where/ how do I test it?

Thanks, Jay.

IAC = Idle Air Control... or some such thingy..

its on the front of your throttle body.. it controls a little pin that moves in and out allowing air to bypass the butterfly.

old_man · May 7, 2004

If you are familiar with using carb cleaner or starting fluid to search for vacuum leaks, that is the easiest method of troubleshooting it. Nobody ever seems to have a vacuum guage anymore for troubleshooting, but its one of my most used troubleshooting tools.

kc7bur · May 7, 2004

I will try cleaning/ checking for more vacuum leaks.
Its weird, it idles fine after its been sitting a while,
when I get to my destination, put it in park, it idles up to 1500.

sidriptide · May 8, 2004

this is the same thing i am having with my 87.. been that way since i gave the engine a super cleaning to get rid of dirt/oil build up.. the TPS doesnt react well to water.. i finally have a new TPS and hope to get it swapped this weekend and see what it does for me...

mike

kc7bur · May 8, 2004

Yep, it started doing this after I cleaned the motor. I used a plastic bag wrapped around the distibutor and used engine degeaser prior to spraying it.
Let me know if the TPS change helps your XJ.

the_bandit87 · May 9, 2004

I have kind of the same thing going on wiht mine, only mine will go really high to like 2800 and push on 3000-3500 for a few seconds after I start it before it calms down and goes to 750. I have clean throttle plates, but an old O2 and TPS sensor, could these be my problem?

fredruss · May 9, 2004

My '88 4.0 has a high idle situation occasionally also. I see references to a potential problem, a "TPS" and that it can be tested with a multimeter. What does TPS mean, where is it located and how is it tested.

Trail-XJ · May 9, 2004

i replaced my TPS because of this problem and it didn't fix it, i am leaning to believe that it is some kind of a temp sensor because it dosen't do it as bad when it's warm. when mine is cold it will go up to 2500 but when it's warm out the highest i have seen is 1500. still trying to figure it out

kc7bur · May 10, 2004

I think I found it, Manifold a tad loose at #6. As a matter of fact, the valve cover was loose. Duh. And Gee, so was the tranny pan. Duuuh.
If the bolts on the valve cover and trans pan would have been tight, I would'nt have gone to the car wash and sprayed. And if I had'nt sprayed the engine, I would'nt have removed all the gunk and created a vacuum leak.

High idle

kc7bur

NAXJA Forum User

89xj

NAXJA Forum User

kc7bur

NAXJA Forum User

RINGKONG

NAXJA Forum User

old_man

NAXJA Forum User

kc7bur

NAXJA Forum User

sidriptide

nobody of any consequence

kc7bur

NAXJA Forum User

the_bandit87

NAXJA Forum User

fredruss

NAXJA Forum User

Trail-XJ

NAXJA Forum User

kc7bur

NAXJA Forum User

Similar threads