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Old 03-25-2014, 06:16 PM   #1
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Join Date: May 2013
Location: Littleton Colorado
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Idle Problem

The Jeep: 1997 TJ Sport 4.0 66k miles. I've changed plugs, distributor cap, rotor, and wires within the last 5k miles. Was running great until yesterday...

Yesterday, out of the blue, the idle started to creep higher and was erratic. Now idling around 1200 RPM. I also noticed that the usual idle kick down when stopping didn't happen at all. Up until yesterday, the car idled at around 800 RPM always. The car didn't throw a code.

I looked at the threads on this site and figured that my problem, after checking for vacuum leaks and not finding any, was the IAC. I removed it today and it was pretty crudded up and I also noticed that the threaded nylon sleeve for the pintle was loose and the threads looked bad. So rather than just cleaning it, I decided to go ahead and replace the whole unit. I also removed the TB and cleaned it up really well at the same time.

Well after almost a whole day wrenching, the problem hasn't gone away. The car still idles around 1150 - 1200 RPM. I pulled the connector for the IAC and got a code then. I cleared the code with my scanner and also tried disconnecting the battery to set the engine controller back to baseline - problem still there. I also noticed that the usual "kick down" in idle when the car rolls to a stop still doesn't occur anymore. I checked the speed sensor with my scanner (real time, while driving) and it appears to be operating just fine.

I'm pretty much stumped now and looking for suggestions. Could it be a bad MAF or TPS? Any suggestions would be greatly appreciated. I don't want to start throwing parts at a problem if I don't have to.

Thanks,
Wayne

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Old 03-25-2014, 06:36 PM   #2
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Check check the TPS. I had the same issue. I ended up having to replace it. Hope it helps!

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Old 03-25-2014, 07:51 PM   #3
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You could try cleaning out your throttle body and checking the sensor on that thing, it could be a buildup or a sensor issue
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Old 03-25-2014, 08:03 PM   #4
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I removed the TB and cleaned it thoroughly. How do you test for a bad TPS?
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Old 03-26-2014, 12:44 PM   #5
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To be completely honest I'm not sure how you could test the TBS
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Old 03-26-2014, 01:07 PM   #6
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Quote:
Originally Posted by BigCooks View Post
To be completely honest I'm not sure how you could test the TBS

An air leak will also cause erratic/high idle. If you can rule out any TPS or IAC issue, then you likely have air getting in at the intake manifold or throttle body.
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Old 03-27-2014, 12:22 PM   #7
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Problem Solved!

As it turns out, a bad TPS was causing my problem. I checked around and was able to purchase an Echlin part (P/N 2-20161) that is made in the USA at my local NAPA store ..... $55. There were cheaper options available, but I try to not buy China or Mexico parts and don't mind paying a little more to help OUR economy. Thanks to the posters who suggested the TPS.
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Old 04-19-2014, 11:03 PM   #8
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Where is this TPS located and what do you have to take out to get to it? I have a high idle too but it seems like fixing it is a crapshoot. People say check for vacuum leaks but not sure where to find it? I see only a couple of vacuum lines and they seem to be OK unless there are other tubings that I don't recognize.

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