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Unread 01-09-2014, 09:03 PM   #1
CamRichTJ99
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1999 TJ Wrangler 
 
Join Date: Jan 2014
Location: oregon city, oregon
Posts: 1
99 tj 4.0 low idle/ wont idle when cold

So I finally bought my first wrangler and I'm trying to get it dialed in now. Currently i am having trouble with the idle. It will sit at the first notch around 300 rpm. It doesn't run rough but when the motor is cold i have to hold the axcel down for a few minutes or it will die.

So here is some background.
When I bought it a few weeks ago it ran fine but the idle would jump around from 1200 to 2000 rpm. I took throttle body off and cleaned it, the IAC, and all of the connecting hoses with Seafoam. this didn't really change much. So then I replaced the IAC all together and now it idles way too low. I've changed the plugs(which were in the worst condition I've ever seen) and the cap and rotor as well. I am currently running Seafoam through the fuel.

is it an issue with the computer or maybe the plug that changes the IAC position? because when i switch the two back and forth the idle will be either way high or way low like the IAC isnt even being moved.

I'm getting a little annoyed with it now and i need some help so
thanks for the help in advance!

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Unread 02-01-2014, 06:49 PM   #2
Jam1965
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1997 TJ Wrangler 
 
Join Date: Apr 2011
Location: Levittown, Pa
Posts: 67
I have had all kinds of issues with aftermarket IAC's, I've changed to a factory IAC and the Jeep runs like new, spend the extra couple bucks and get the right part.
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Unread 02-01-2014, 09:59 PM   #3
oakmckinley
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1999 TJ Wrangler 
 
Join Date: Mar 2010
Location: Minneapolis, MN
Posts: 1,519
What codes are you getting from the CEL? I am assuming its on. If its not on that would surprise me.
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Unread 02-02-2014, 05:27 AM   #4
Jonny Jeep
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1997 TJ Wrangler 
 
Join Date: Feb 2007
Location: Manchester, UK
Posts: 4,801
Having to hold the accelerator down for a while to stop the engine dying could be an indication of a bad battery. If the battery is bad it could cause rough running and idle problems.
Get the battery charged up using a bench charger and then go and get it load tested.
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Online factory service manuals (FSMs) and parts lists can be viewed at http://www.jeep4x4center.com/knowledge-base/index.htm
If the link doesn't work properly, look for the service manual link under Jeep Resources at the bottom of the page.
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4.0 , low idle , no idle

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