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Unread 10-09-2008, 12:31 PM   #1
Chad184
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1999 TJ Wrangler 
 
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4.0 stalls occansionally when RPMs drop quickly

I have a 98 Sahara Edition and it tends to stall when the RPM's are above 2,000 and I lift my foot of the pedal. I'm a new Jeep owner, have had it off road every weekend since I bought it - so much fun, but am worried I might have an idler problem, or in need of a cat replacement.

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Unread 10-09-2008, 03:01 PM   #2
Jerry Bransford
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That problem is generally/usually caused by a dirty IAC (idle air controller). The IAC is mounted to the passenger side of the throttle body and is responsible for providing all of the engine's air when at idle and the butterfly valve is closed (when your foot is not on the accelerator pedal).

The IAC gets dirty over time and when it does, it can't open smoothly enough so it won't provide engine air well enough for a smooth idle.

Held on by two small torx-head bolts, the IAC is easily removed and cleaned... there is usually no need to replace it. Buy an aerosol can of throttle body cleaner and with a rag and/or toothbrush, gently clean the IAC's solenoid actuated plunger which is what fits into the throttle body to control the amount of air that gets into the throttle body. Don't push/pull/twist/turn that plunger. Clean the oriface the plunger fits into too. Once the IAC is clean and reinstalled, use the rest of the throttle body cleaner to clean the inside of the throttle body per the instructions on the can.

Here's a diagram showing where it is. Notice that slot labled "Idle Air Control Passage Inlet"? That's where the TB gets its air through at idle as controlled by the IAC. Good luck and a big welcome to JF.
iac.jpg  
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Unread 10-09-2008, 03:04 PM   #3
TheBoogieman
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That covered it and welcome.
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Unread 10-09-2008, 10:16 PM   #4
Chad184
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WOW! Thanks for the quick reply. I looked at it tonight and will be able to clean it this weekend (not a daily driver) as long as the snow melts a bit.
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Unread 10-10-2008, 12:54 AM   #5
97casteeltj
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Quote:
Originally Posted by Chad184 View Post
WOW! Thanks for the quick reply. I looked at it tonight and will be able to clean it this weekend (not a daily driver) as long as the snow melts a bit.
its 70*+ here!!! i wonder when it will cool off!!

-John
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