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Unread 01-11-2009, 05:56 PM   #1
WVjeep94
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4.0 idling issues

When i first start up my 94 it idles and runs fine. Once you take it down the road for a while and come to a stop the idle jumps to about 1500 with the clutch in or if you take it out of gear. If you shut it off and let it sit for a little bit it starts up and idles fine again. Ive cleaned the throttle body with a rag and some throttle body cleaner and have also replaced the throttle positioning sensor. What should i do next?

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Unread 01-11-2009, 06:06 PM   #2
laybackman
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I would guess that the Idle Air Control (IAC) could be dirty also it is in the Throttle body also. Two torx screws hold it in place I beleive. Mine idled poorly so I pulled the IAC cleaned it and the bore it sits in with carb cleaner. Just be careful that the probe on the IAC does not get pulled out or it is junk. Clean the rpoobe preotion with CC and steel wool.
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Unread 01-21-2009, 06:23 PM   #3
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Alright I cleaned the throttle body got a new IAC and TPS and am still idling after running for a little bit at about 1200-1500. I pulled it in the car port opened the hood and could get the idle to come down to normal by putting a litte pressure on the butterfly on the throttle body. Can I replace the spring on that thing or what else could it be?
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Unread 01-21-2009, 07:00 PM   #4
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Alright I cleaned the throttle body got a new IAC and TPS and am still idling after running for a little bit at about 1200-1500. I pulled it in the car port opened the hood and could get the idle to come down to normal by putting a litte pressure on the butterfly on the throttle body. Can I replace the spring on that thing or what else could it be?
You got three cables going to the TB. Are any of them binding up?

The spring on the throttle arm whiuch is opposite the TPS might need a shot of carb cleaner then a shot of lube like silicon spray.
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Unread 01-21-2009, 07:07 PM   #5
WVjeep94
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That might be my problem right there I only have one cable going to the throtte body. Is there supposed to be more than one spring too? I think i might need a picture.
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Unread 01-21-2009, 08:12 PM   #6
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So you have the cable from the gas pedal what other cables are supposed to be on there?
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Unread 01-21-2009, 08:40 PM   #7
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So you have the cable from the gas pedal what other cables are supposed to be on there?
Just the one. You could have three, if there were a cruise control cable, and a kickdown cable for an automatic tranny, but you probably won't have but the one.

The OE spring should be plenty, but you can add another if you like, it won't hurt anything, it'll just make for a stiffer throttle pedal & possibly a numb right leg.

Check thoroughly for a vacuum leak. Any "un-metered" air between the throttle plate & cylinder head will raise your idle. The more significant the leak, the higher the uncontrollable idle will be.


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Unread 01-21-2009, 08:46 PM   #8
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Wouldnt a vaccum leak or unmetered air cause it to do this all the time right at start up? Instead of going away if you shut it off and wait a few minutes and start it back. When i shut it off for a little bit i can start it back up and it idles fine.
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Unread 01-21-2009, 08:53 PM   #9
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A "cold/cool" engine will idle lower & require more air to maintain the correct idle. This may explain why it idles okay when first started. A warmer engine (after having gone down the road a little way, as you described) would require less air (like from the idle motor circuit) to maintain correct idle. A small vacuum leak could be allowing just enough air into the intake so that the idle motor can't cut enough air out to compensate. In this time of year when the engine cools off so much faster after shut down, the problem my become a bit more invisible.
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Originally Posted by UltimatE View Post
Max has a picture of every Jeep part ever made.
Quote:
Originally Posted by Benderff View Post
No one here knows what they are talking about. You should try Pirate 4x4 they will be happy to help you.

There is no situation that cannot be improved with a small but well-placed explosive.
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Unread 01-21-2009, 09:04 PM   #10
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thanks for the reply Ill take a look tomorrow
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Unread 01-21-2009, 09:15 PM   #11
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thanks for the reply Ill take a look tomorrow
If you spray some throttle body cleaner arond your vacuum fittings & lines while it's running, the leak can usually be detected by listening for the idle to fluctuate as it sucks up the cleaner through the leak.

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Quote:
Originally Posted by UltimatE View Post
Max has a picture of every Jeep part ever made.
Quote:
Originally Posted by Benderff View Post
No one here knows what they are talking about. You should try Pirate 4x4 they will be happy to help you.

There is no situation that cannot be improved with a small but well-placed explosive.
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Unread 01-22-2009, 07:03 AM   #12
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That might be my problem right there I only have one cable going to the throtte body. Is there supposed to be more than one spring too? I think i might need a picture.
EDIT EDIT You MAY have UP TO three cables on your TB. I am dummy for not makiing that clear. Try cleaning the spring then check the MAP sensor vacuum hose and start looking for any leaks with spray as mentioned a loose TB etc. Did you check for any trouble codes?
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Unread 01-22-2009, 06:00 PM   #13
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I figured it out today, I had a couple intake manifold bolts loose. Tightened them up and it seems to be doing fine now. Thanks
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Unread 01-23-2009, 02:09 PM   #14
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I figured it out today, I had a couple intake manifold bolts loose. Tightened them up and it seems to be doing fine now. Thanks
That would be the vacuum leak then!

Glad you got it all sorted out, and posted your findings/results! You may be helping somebody else out in the future!



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Quote:
Originally Posted by UltimatE View Post
Max has a picture of every Jeep part ever made.
Quote:
Originally Posted by Benderff View Post
No one here knows what they are talking about. You should try Pirate 4x4 they will be happy to help you.

There is no situation that cannot be improved with a small but well-placed explosive.
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