Question: Need Help!!!!... TJ Idle Issue -
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post #1 of 3 Old 06-09-2012, 03:32 PM Thread Starter
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Question: Need Help!!!!... TJ Idle Issue

Hoping for some help/insight -- suggestion!

1999 Sahara 4.0l 6cyl a/t

***Idle issue: [i think!]
- when I shift from "drive" to "park" the idle sometimes revs upwards of 2500 rpms. Trying to kick it down rarely has any effect. When I shift there's usually quite a clunk - and if I don't have my foot firmly on the brake the thing might just slam into the car parked in front of me [more on this below].
For the most part, doesn't happen on cold start - but jeep doesn't need to be warmed up for it to happen [ie. i can start it when cold, drive 100 feet, put it in park and it could happen].
Problem has gotten progressively worse used to happen on occasion - now happens more times than it doesn't.
- other symptom [which i assume is related and made reference to above]: once I take my foot off the brake [when in 'drive' or reverse and stopped] - the jeep takes off on its own.
this started happening about the same time that the high rpm issue got worse. I've basically wore down my brakes just from sitting at a stop light.

Had someone tell me its likely a vacuum leak and I should let the engine run and spray carb cleaner all around the intake to check? [no idea if this is the thing to do]!

Also have read that it's likely either the IAC [which should be pulled and before buying new] -- or the TPS.

Any troubleshooting advice or diagnostic expertise would be greatly appreciated.

And if there is any other info you need in order to nail it down, please ask!!!


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post #2 of 3 Old 06-09-2012, 04:08 PM
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Yes, spraying starting fluid around the intake/major vacuum lines at idle is ok. Idea is if there is a vacuum leak it will draw the starting fluid in and the idle will change identifying the leak. TPS and IAC will also affect idle. A sticky IAC will raise idle. If it is sticking open.

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post #3 of 3 Old 06-09-2012, 04:25 PM
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Sounds freakishly similar to problems with my wife's Ford escape we struggled with for about a year and thousands of dollars in most likely needless repairs. I imagine yours would have to be more straightforward, but while you're in there, you might as well take a look at your battery terminals and cables.

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automatic , idle , rpms , shift , tj

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