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Unread 09-04-2012, 07:57 PM   #1
rylo0421
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Hugh idle.... Where to start?

Hello all, had a high idle on my 97 wrangler 2.5 inline 4. Got higher and higher as the drive went on until I got home and it was idling at 2200ish and threw the check engine light..... Where do I start? Have read lots about TPS, IAC, throttle body and intake. Any input is appreciated. Thanks.

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Unread 09-05-2012, 12:20 AM   #2
Jkanly
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Quote:
Originally Posted by rylo0421
Hello all, had a high idle on my 97 wrangler 2.5 inline 4. Got higher and higher as the drive went on until I got home and it was idling at 2200ish and threw the check engine light..... Where do I start? Have read lots about TPS, IAC, throttle body and intake. Any input is appreciated. Thanks.
Something is letting too much air into the intake. I would check all your vacuum lines for leaks.

One of the classic ways to do this is while the engine is running spray some starting fluid around the area where the vacuum lines are or around the intake itself. The engine should change/raise in rpm when an opening is found letting extra fuel into the intake.

If you've got an engine light on, that's basically the engine trying to tell you what the problem is. All you need to do is read it at an auto parts store. They should do it for free.

I also had this problem when some squirrels got into my intake and stored their acorns in the opening on my throttle body butterfly. About half way down the road an acorn got jammed and the throttle stuck open. Good times
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Unread 09-05-2012, 07:37 AM   #3
rylo0421
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Thanks Jkanly. It seems to slowly raise in RPM even just sitting in neutral. I will check all the lines and intake.
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Unread 09-05-2012, 10:01 PM   #4
jnicewan
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Get the PCM scanned for codes, there is a good chance a sensor has failed causing the idle concern and ck eng light.
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Unread 09-06-2012, 07:48 AM   #5
rylo0421
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I disconnected the battery for a while and the code cleared. So it's just idle that is my concern right now. I was sure that something had failed after driving for a while and thats why the CEL came on. Am leaning more towards a sensor based on that. TPS was held in place with electric tape when I picked the jeep up. Cleaned it and got no results.
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Unread 09-06-2012, 03:34 PM   #6
mjmurphy926
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You should always check for codes when the CEL comes on. It's easy. With the car turned off, do the following sequence with the key in the ignition switch:
on-off-on-off-on

Any codes in the PCM will display on your odometer. Google the codes and address the problem.

EDIT - I should add that the above sequence works on my 04 TJ. Not sure what else it works on.
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Unread 09-08-2012, 10:24 PM   #7
rylo0421
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I tried the ignition sequence, it didn't work. I found a leak in the intake/exhaust manifold by using the old starter fluid test. Replaced the gasket today and got some result. Idle isn't near as high but still at around 1200RPM after driving. When I come to a stop it lowers to around 1000. I'm thinking IAC? TPS? Any ideas or similar experiences. Again it's a 97 TJ 2.5 4 cyl. Thanks and appreciate your input.
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Unread 09-09-2012, 12:52 AM   #8
jnicewan
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After the repair, go ahead and unplug the battery again for a few minutes to reset the pcm, it probably wont help but this step costs you nothing Also it might be a good idea to clean the throttle body, IAC and IAC passage. Also if somebody else has been messing with the idle, maybe they screwed the idle stop screw in and it needs to be backed out a little.

IAC or TPS can cause idle issues like this, along with a vacuum leak, which you probably fixed and have no others. Do a search for cleaning the IAC and T/B and if not then simply remove the IAC and clean the tip, along with cleaning the passage the IAC goes into, then manually open the throttle and clean the housing and throttle plate. Any decent carb cleaner and an old tooth brush and rag should be all you need.
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Unread 09-09-2012, 07:44 AM   #9
rylo0421
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Jnicewan- thanks all good stuff. I had the battery disconnected all day while I replaced manifold and did tranny, radiation flush. So it was disconnected for most of the day. Do you think it will help to try again since I reconnected and drove with new manifold gasket? I was also thinking it might help after the gasket had been heated and driven with to help seal real good? Something I have always thought but no proof. I am definitely going to focus of IAC. Need to check that stop screw tho. Thanks again my friend.
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Unread 09-09-2012, 01:15 PM   #10
Jkanly
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The gasket does not need to be broken in. In most cases it's an open or damaged vacuum line, but at this point I would suspect the TPS to be the culprit of the problem, or as the comment above me has stated the IAC is a possibility also
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Unread 09-09-2012, 07:57 PM   #11
rylo0421
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Great news! (for me anyways) High idle is officially fixed. Had ECM read. All sensors passed. So started a meticulous search for a vacuum leak. Found a whole in one of my intake vacuum lines. All in all, only spent the money for a new exhaust/intake manifold which was needed anyway. Thanks for all of the advice. Resting at ease.
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