Idle Problems - JeepForum.com

 
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post #1 of 9 Old 09-27-2002, 09:30 PM Thread Starter
JeepGuyRyan
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Idle Problems

First off, where should the idle be on a 93 GC with the 4.0?

Second, what do you recomend for a rough idleing Engine? It only has 20,000 orig miles on it, recently had a tune up, (didn't seem to help much) It is very annoying to have the thing shaking so much at idle as if it is almost going to stall out.


-=Ryan=-
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post #2 of 9 Old 09-28-2002, 09:43 PM
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My father has a '93 -- I believe I recall him saying there's actually an idle screw on the throttle body. I believe he said it's covered by a little plug, which you can remove and replace after adjustment. I know for a fact there was one on the '87 4.0L engine I once had, but that would have been Renix throttle body, and yours is a different, larger bore throttle body. Still check to see if you can find the idle screw.

The throttle body may need to be cleaned out. Also the idle air control motor on the throttle body may need to be cleaned out. I believe it can simply be removed from the throttle body and sprayed out with carb cleaner. Of course, that IAC might actually be malfunctioning now.

Even with low miles, it's still 10 years old, so it could probably use a new cap & rotor if that wasn't done at the tuneup, along with new plugs and plug wires.

-- Marcus
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post #3 of 9 Old 09-29-2002, 11:31 AM
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Update: Talked with my father this morning -- he said the screw is there but it's JB-welded or otherwise locked in place, not adjustable. I know on the older 4.0L's it was adjustable, but I guess when they went to the Chrysler FI they took care of that.

-- Marcus
Cape Canaveral, Florida
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2005 Dodge Durango SLT 4.7L
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post #4 of 9 Old 09-29-2002, 02:32 PM
Big Dumb White Guy
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nope. it's some kind of loc-tite stuff. take the TB off and clean it and try to adjust it. i tried and it has made no difference. still idles like crap!

repost Nazi's suck!

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post #5 of 9 Old 09-29-2002, 04:10 PM
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You can use a voltmeter to test the AIC -- it's supposed to return a specific voltage range when closed versus open, I believe. Have to check the manual. My father's '93 GC did have a bad AIC at one time that he diagnosed that way -- the voltages were way off.

-- Marcus
Cape Canaveral, Florida
2005 Jeep Grand Cherokee Laredo 4.7L
2005 Dodge Durango SLT 4.7L
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post #6 of 9 Old 09-30-2002, 06:15 AM
ALS59LTD
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the idle is controlled by the computer with the IAC (Idle Air Control) valve. you should check/replace the valve. they can get pretty expensive. I remember the one for my camaro was like $70.

Where did you find a 93 with 20,000 miles??????

-Alex
http://www.jeepforum.com/forum/f22/turbocharged-2-4l-jeep-tj-me-too-2255329/
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post #7 of 9 Old 09-30-2002, 06:22 AM
Big Dumb White Guy
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Autozone was like under $60.

repost Nazi's suck!

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post #8 of 9 Old 09-30-2002, 03:56 PM
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Yeah, a '93 with 20,000 actual miles would be a pretty sweet deal if it's in good shape.

-- Marcus
Cape Canaveral, Florida
2005 Jeep Grand Cherokee Laredo 4.7L
2005 Dodge Durango SLT 4.7L
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post #9 of 9 Old 10-03-2002, 07:42 PM
rebrock57
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My 94 4.0 had a rough idle, it turned out that the stock motor mounts had weakened, allowing the engine vibrations to be transmitted through to the frame and body, Replaced the motor mounts and it idles as smoothly as new, now with 156k miles.
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