Help! 4.0 dies when in idle - JeepForum.com

 
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post #1 of 3 Old 08-16-2009, 10:18 PM Thread Starter
4LiterFury2010
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Help! 4.0 dies when in idle

Well all of this began about a week after I installed a cat back exhaust kit. It started by simply just shutting down when the engine was on while left in park for about five minutes. Now it kills much faster and often come close to killing when I decelerate and reach low RPMs. The problem is making it nearly impossible to drive anywhere now. Only strted a day ago so its not like i've been driving it everywhere while it's been like this. Could the new exhaust have caused this? maybe just coincidence? My engine has had a strange habit of eradic RMP's shortly after start up that caused it to run pretty rough for a couple seconds before the RPM's shoot up and then runs fine. Bad fuel pump or cloged fuel filter? Or maybe just an engine adjustment do to higher exhaust flow? I'm truly puzzled so any input is welcome. Thanks!

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post #2 of 3 Old 08-16-2009, 11:55 PM
Jerry Bransford
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When the engine dies only at idle, that's usually a sign it's not getting the air it requires through the IAC's (Idle Air Controller) Passage Inlet. Cleaning the throttle body's interior with a throttle body cleaner while the engine is running, taking particular care to aim some of the spray at the IAC Passage Inlet as shown in the below illustration, usually takes care of the issue. Sometimes the IAC has to be removed to be cleaned more thorougly if cleaning it through the throttle body doesn't take care of it. The IAC is a solenoid actuated plunger that allows air into the engine via the IAC Passage Inlet at idle rpms when your foot is off the accelerator pedal that leaves the TB's butterfly valve plate closed. Without the IAC letting air in at idle, the engine won't run or it will idle erratically.
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post #3 of 3 Old 08-17-2009, 03:15 PM Thread Starter
4LiterFury2010
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I thought that it very well could have been the throttle body, but I just took it in to get it looked at because I need school transportation starting tomorrow. It turns out that it was a bad cam shaft sensor I never would have thought of that in a million years. It is appearently a fairly common issue with chrysler engines, but I dont know anybody or have even heard of anybody for that matter that has had this problem. Anyone on here ever experience this?
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