97 TJ is idling high, what's wrong? - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 04-17-2002, 07:31 AM Thread Starter
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97 TJ is idling high, what\'s wrong?

My 2.5L TJ is idling high. It stays around 2000 RPM when shifting. If I let it sit and run it goes down to about 1100, then it jumps back up to 2000 again. Sensor? I don't know.
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post #2 of (permalink) Old 04-17-2002, 09:25 AM
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Re: 97 TJ is idling high, what\'s wrong?

Humm... Perhaps it's a bad idle air control motor or a vacuum leak. If the maifold starts suckin' air then the air fuel mixture is thrown off and the computer compensates (within reason) for the leaned mixture by increasing the on-time of the injectors. This enriched condition lets the engine ilde higer than normal. Have you seen any drop in MPG?

The first thing I'd do is pull the IAC and clean it up. Often it's carboned up or the pintle is not able to retract or close off the air port. Simply by cleaning the IAC motor you my solve the problems.

Then if that doesn't work you may want to spritz some water from a spray bottle around the throttle body and the manifold. If the RPM decreases you've found a leak and then just narrow down the area of leak. It's no different than finding a leak on a Carb'ed engine... just less to worry about.

If you haven't checked the computer codes... it may be a good idea to check the computer codes to see if one's been thrown. The codes for the 97 can be found <a target="_blank" href=http://www.webejeepin.com/Check-Engine.htm>HERE</a>.

It's a start... let us know what you come up with.
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post #3 of (permalink) Old 04-17-2002, 10:47 AM Thread Starter
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Re: 97 TJ is idling high, what\'s wrong?

I haven't noticed a decrease in MPG, but I have noticed that it acts sluggish when it is cold. This sluggishness acts like a rich running carb would, it bogs down when I initially hit the throttle. I have also noticed that my throttle seems to "catch" fairly often. It feels like a mechanical catch, like the cable could be starting to fray somewhere. Is there something in the IAC that would hang up and cause this "catch" ?
The idling problem just started Sunday, but the "catch" has been going on for about six months. I figured I would have to idle home sooner or later when the cable broke, but maybe that's not the case at all. Maybe this IAC has been giving me problems for six months, and I didn't diagnose it properly. I should have asked the bbs sooner!
I will repost after I clean this thing up. Probably this weekend.
thanks!
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post #4 of (permalink) Old 04-17-2002, 12:27 PM Thread Starter
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Re: 97 TJ is idling high, what\'s wrong?

Checked for codes in the PCM. Got nothing but a 55, completion of the test.
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