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Old 10-08-2010, 07:17 PM
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High idle problems

Hi posted this on another forum but havent had any luck on any new info was hoping someone here might be able to give advise.

Hoping someone can give some advise, just got 2004 wj 4.0. It has 12100 miles on it. As I was driving home from where I bought it, the check engine light came on, stop and had code read.The code was 601 everything on the car worked great.
Got a rebuilt or flashed pcm from AUTO COMPUTER EXCHANGE car ran great for a few days and then started with low idle almost to a stall or high rpms over 1500. have been reading on the tps and iac valves as well as cleaning throttle body, so I first cleaned out iac, tps as well as throttle body but no improvement, then replaced tps, now car no longer has low rpms but idling at about 1000 rpms, next step was to replace iac motor and now car is idling at 1200 if I put in gear car idles at around 1500 rpms if I turn on air it drops down to about 900 rpms. Guess my question is it possible I'm having a problem with the pcm again even though it isn't showing any codes. problem is intermittin, had car checked for vacuum leak. They couldnt find any. Totally lost at this point nay help will be appreciated.
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Old 10-08-2010, 07:56 PM
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Re: High idle problems

Did you disconnect the battery before installing the new IAC? When you have changed the IAC and connect the battry again, the IAC stepper motor will be driven to fully closed and then fully open (or the other way around), for the PCM to remember those positions.
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Old 10-08-2010, 08:27 PM
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Re: High idle problems

yep...resett the pcm
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Old 10-08-2010, 08:37 PM
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Re: High idle problems

Thanks for your reply, I did and also had read to disconnect positive batt and ground the pos to ground to reset pcm in hopes to get the pcm to relearn the sensors. But it still comes up with about 1500 rpms if I turn on air it drops to about 1200.
if I kick it to drop rpms it goes to 2500 and will not drop so I have to turn it off, I am wondering since problem is intermittent it could be the pcm it is a rebuilt one I spoke to them and they said to check for vacuum leak. I took it to a local shop and they spent over an hour looking for leak and couldn't find one. I watch as they had 3 different guys look. Frustrating
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Old 10-08-2010, 08:42 PM
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Re: High idle problems

get another pcm...thats one is fubered
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Old 10-08-2010, 08:43 PM
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Re: High idle problems

So you think it may be the rebuilt pcm?
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Old 10-08-2010, 08:56 PM
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Re: High idle problems

Pcm's for 2004 WJ's are all reman units. They take the old ones, and recore them (new boards)

You said it's a 4.0L.
Check the vacuum lines on the intake manifold, they are located on the side of it, in the center
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Old 10-08-2010, 08:59 PM
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Re: High idle problems

Also, resetting the PCM, via the grounding method will not correctly relearn the IAC steps. You really need a DRBIII to correctly relearn the IAC. Additionally, you may want to remove the throttle body and remove the IAC rom it. Check the passage for a carbon build up. I would clean the T-body and the passage for the IAC, as wel as the pintle for the IAC plunger.

Just my 2cents as a Chrysler Tech ..
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Old 10-08-2010, 09:05 PM
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Re: High idle problems

Had local shop check for vacuum leaks and they were unable to find one, this problem is intermittent, had replaced pcm because of a p0601 code If I remember right, which was a
Internal Controller Failure Internal control module fault condition (check sum) detected The jeep ran perfectly except for that code. After the pcm was replaced it ran great for about 5 to 7 days then the problems started.
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Old 10-08-2010, 09:08 PM
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Re: High idle problems

Would just letting it go tru the 20 cycles cause the pcm to relearn it?
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Old 10-08-2010, 09:14 PM
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Re: High idle problems

Jeep has new tps, iac, throttle body has been pulled and cleaned at local shop as well as they looked for more than an hour for vacuum leaks to no avail. Is it possible the pcm is the problem, don't know much about this I did notice my old pcm was a rectangle box and the new one was not like a box but had like leg like things were mounting screws go tru I asked if that made a difference and was told it didn't, to me it seemed the one I got was older, but what do I know.
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Old 10-08-2010, 09:32 PM
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Re: High idle problems

Quote:
Originally Posted by farefax View Post
Jeep has new tps, iac, throttle body has been pulled and cleaned at local shop as well as they looked for more than an hour for vacuum leaks to no avail. Is it possible the pcm is the problem, don't know much about this I did notice my old pcm was a rectangle box and the new one was not like a box but had like leg like things were mounting screws go tru I asked if that made a difference and was told it didn't, to me it seemed the one I got was older, but what do I know.
PCM for your vehicls should look like the original one.
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