Help! 4.0 dies when in idle -
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back > Models > Jeep Wrangler Forums > TJ Wrangler Technical Forum > Help! 4.0 dies when in idle

Save 17.76% for the 4th of july with ruffstuff specialtiesUCF Independence Day Savings... Save 15% today!The Original 3/8" Ruffstuff Diff Cover!

Unread 08-16-2009, 10:18 PM   #1
Registered User
2000 TJ Wrangler 
Join Date: Jan 2009
Location: Indianapolis, IN
Posts: 96
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!

4LiterFury2010 is offline   Reply With Quote Quick reply to this message
Unread 08-16-2009, 11:55 PM   #2
Jerry Bransford
Jerry Bransford's Avatar
2004 TJ Wrangler 
Join Date: Jan 2003
Location: Escondido, California, California
Posts: 62,092
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.
Getting Savvy...

Coolest offroad magazine ever! CRAWL Magazine

When you have a choice, buy American.
Jerry Bransford is offline   Reply With Quote Quick reply to this message
Unread 08-17-2009, 03:15 PM   #3
Registered User
2000 TJ Wrangler 
Join Date: Jan 2009
Location: Indianapolis, IN
Posts: 96
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?
4LiterFury2010 is offline   Reply With Quote Quick reply to this message

Quick Reply

Register Now

In order to be able to post messages on the forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.
Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.
Note: All free e-mails have been banned due to mis-use. (Yahoo, Gmail, Hotmail, etc.)
Don't have a non-free e-mail address? Click here for a solution: Manual Account Creation
Email Address:


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Thread Tools

Suggested Threads

Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. is not in any way associated with Jeep or the Chrysler Corp.