idles at high rpm
Thread Starter
Junior Member
Joined: May 2010
Posts: 37
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From: Portland Oregon
Year: 92
Model: Cherokee
Engine: 4.0l
idles at high rpm
My 88 renix runs great...for the most part. Sometimes when I start it up it wants to ilde at like 3000! If I cycle the key on and off a few times and restart it, it will idle normal. It dosent matter hot or cold seems totally random. Any ideas
CF Veteran
Joined: May 2009
Posts: 10,423
Likes: 61
Year: 2000
Model: Cherokee (XJ)
Engine: 4.0
Mine does it too.
New IAC would most likely fix your problem, I would also look for vacuum leaks around the intake manifold/head surface.
If you know how to do it, you may need to also adjust/check your TPS.
New IAC would most likely fix your problem, I would also look for vacuum leaks around the intake manifold/head surface.
If you know how to do it, you may need to also adjust/check your TPS.
CF Veteran
Joined: Nov 2010
Posts: 5,840
Likes: 117
From: In the middle of Minnesota!
Year: 1999
Model: Cherokee
Engine: 4.0
Great advice.
A vacuum leak and a faulty or dirty idle air control are the #1 and #2 suspects here.
Sometimes cleaning of the idle air control will restore function as they get carboned up over time and miles. SEARCH.
A vacuum leak and a faulty or dirty idle air control are the #1 and #2 suspects here.
Sometimes cleaning of the idle air control will restore function as they get carboned up over time and miles. SEARCH.
CF Veteran
Joined: May 2009
Posts: 10,423
Likes: 61
Year: 2000
Model: Cherokee (XJ)
Engine: 4.0
My writeup from a different forum.
You can try cleaning it, mine idled better for a while and then started doing it again so its time for a new IAC. (actually just a whole new jeep)
you can also take off the whole TB and clean everything but its kind of a pita.
You can try cleaning it, mine idled better for a while and then started doing it again so its time for a new IAC. (actually just a whole new jeep)
you can also take off the whole TB and clean everything but its kind of a pita.
IAC Cleaning (Possible fix for High Idle)
I have been having high idle problems lately (1000rpm regular idle, 3000rpm idle on some starts) and decided to clean my IAC to see if it would fix my problem.
Tools: T-15 Torx, Brake cleaner, Q-tips, Rag/Paper towels.
First, locate your IAC. It is located on the TB to the left of the tps, and has a right-angle plug on it.
Remove the two bolts and take out the IAC
The plunger on mine was gunked up with Carbon/oil. I cleaned it using a piece of paper towel and rubbing alcohol at first, I then used paper towel and brake cleaner.
Next I sprayed down the whole IAC with brake cleaner, let it dry, and did this two more times.
While letting the IAC dry, I cleaned the port that it goes into with brake cleaner sprayed onto a q-tip. I went through about 5 before they started coming out slightly clean. keep going till it becomes clean
Put the IAC back on, and plug it in.
Start the jeep, let it idle or take it for a ride. This is just a function check to make sure the IAC is working correctly.
My jeep idles smoother and the idle has dropped to ~800rpm which is pretty much where its supposed to be. If this does not help, you most likely have other problems like a vacuum leak or bad TPS.
Tools: T-15 Torx, Brake cleaner, Q-tips, Rag/Paper towels.
First, locate your IAC. It is located on the TB to the left of the tps, and has a right-angle plug on it.
Remove the two bolts and take out the IAC
The plunger on mine was gunked up with Carbon/oil. I cleaned it using a piece of paper towel and rubbing alcohol at first, I then used paper towel and brake cleaner.
Next I sprayed down the whole IAC with brake cleaner, let it dry, and did this two more times.
While letting the IAC dry, I cleaned the port that it goes into with brake cleaner sprayed onto a q-tip. I went through about 5 before they started coming out slightly clean. keep going till it becomes clean
Put the IAC back on, and plug it in.
Start the jeep, let it idle or take it for a ride. This is just a function check to make sure the IAC is working correctly.
My jeep idles smoother and the idle has dropped to ~800rpm which is pretty much where its supposed to be. If this does not help, you most likely have other problems like a vacuum leak or bad TPS.
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