'97 tj high idle

Neskie Crawler

Neskie Crawler

TJ Enthusiast
Joined
Dec 26, 2015
Messages
153
It just popped into my mind that this past summer when I bought my 1st Jeep, while off road and only while steep hill crawling in 4H or 2wd going at very low speed I noticed I could take my foot off the pedal and She will idle up to the top steady and then on level, a fairly high idle, I didn't ck the tach, but a fairly high rev that goes away after the motor cools some w/fresh air. I've got good coolant and of course the direct drive fan always runs. I've had the motor hot plenty of times but that is the only scenario where this happens. Thoughts? I'm only a backyard mechanic at best but thinking an o2 sensor or computer? thanks.
 
UPJOHN said:
Your idle air motor might be dirty. I took mine off the throttle body and cleaned it with a tooth brush and a little gasoline.
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X2

This is the very first thing you should check (and clean) when diagnosing a high idle issue. The IAC is notorious for getting gunked up and making the idle high on these wranglers.

Clean it and see if that solves your issue. If that's not the issue then I would report back. Just trying to start with the simplest scenario.
 
Thank You for the quick replies. So that could make it idle higher just on occasions like I described? Is it pretty easy to take off and get to?
 
Neskie Crawler said:
Thank You for the quick replies. So that could make it idle higher just on occasions like I described? Is it pretty easy to take off and get to?
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Yes, very easy to take off and get to. When the IAC is gunked up and dirty the number one sign is always higher idles which can happen constantly or just on occasion.

This is a common issue so I'll post a how-to guide for this tonight on the forum and make a link to it in this thread
 
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That is SUPER cool. That will help me out and if it so common I hope it helps many others out as well. Awesome.
 
Neskie Crawler said:
That is SUPER cool. That will help me out and if it so common I hope it helps many others out as well. Awesome.
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It's very common so it should be a how-to anyways. I'm trying to get as many how-to articles as possible for the more common issues like this one. I know one other member (maybe it was @UPJOHN?) was having this idle issue a few weeks back and cleaning the IAC fixed the issue.
 
Chris said:
It's very common so it should be a how-to anyways. I'm trying to get as many how-to articles as possible for the more common issues like this one. I know one other member (maybe it was @UPJOHN?) was having this idle issue a few weeks back and cleaning the IAC fixed the issue.
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Back in September when I first got my TJ my check engine light was on, and showing a code #25 IAC. It idled too fast then too slow. I cleaned the IAC, the light went out, and my idle is now perfect.
 
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UPJOHN said:
Back in September when I first got my TJ my check engine light was on, and showing a code #25 IAC. It idled too fast then too slow. I cleaned the IAC, the light went out, and my idle is now perfect.
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Yep, that's what I thought. Usually the IAC is the issue.
 
Thanks, UPJOHN. And interesting as well as no ck engine light goes on in my case. My dash lights do work at the turn of the key but no instrument panel lights work at night with the headlights. I'm not even interested in tracking that issue down but can't wait to find exactly how to tackle the IAC issue. And time is no issue; it did not alarm me enough when it happened 2-3 x and I prob won't get to fixin it immediately either but will most def let everyone know results.
 
Here you go: How to clean your IAC valve

Honestly, this is one of the simplest and easiest things you can do. Once you do it see if it solves your idle issues. If it doesn't, then it's time to keep looking for the culprit. However, this will at least eliminate the cheapest (and most common) of the idle associated culprits.
 
It is always goo to know how far open the IAC is at idle. If it is way open, this leads to the engine slowing as you pull away from a stop. It is still in the control loop and trying to bring the idle down. Upside of adjusting your butterfly to minimize the IAC at low speed is the benefit of it opening during slow crawling to keep you idle steady.
 
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