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Old 10-24-2012, 05:21 PM   #1
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Engine dies when idling

My jeep will crank but when Im at a complete stop it will just shut off. It drives normal but once i come to a complete stop at a stoplight or stop sign it will die. I have to feather the gas just to keep it running. It starts and idles fine in the mornings but once the engine warms up it will dies at stops. Anyone else have this problem before?

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Old 10-24-2012, 08:12 PM   #2
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sounds like your Idle Air Control is going out if it is just having trouble idling and has no other problems with running.

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Old 10-24-2012, 08:25 PM   #3
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This happened on my '01 WJ when the 4.0L had about 135,000 miles. There were no codes or CEL. The cure was to take off the throttle body and clean out all the little idle air passages on the workbench with solvent and little brushes about the diameter of pipe cleaners.

The cause is excessive vapor and fumes from the PCV into the air cleaner, but the mechanic said compression was still good and we were a long way from needing a ring job. It was a $120 repair, all labor. I might need the same thing once or twice again before an engine rebuild, was the comment.
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Old 10-24-2012, 08:28 PM   #4
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I'd say the Idle Air Control is probably dirty and needs cleaning with some aerosol throttle body cleaner, seldom does the IAC need to actually be replaced when that happens. The IAC is what provides virtually all of the engine's air at idle RPMs when your foot is off the gas pedal. That it runs ok with a little bit of pressure on the pedal seems to confirm that.

Battery is ok right?
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Old 10-24-2012, 08:35 PM   #5
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Alright ill pick up some cleaner tomorrow and give it a try. Any advice on cleaning it?

Also,the battery is in good shape.
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Old 10-24-2012, 08:43 PM   #6
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The IAC sucks air through its Idle Air Control Passage Inlet slot (see below) only at idle RPMs. Therefore, it can only suck in the Throttle Body cleaner at idle RPMs. What you want to do is to get cleaner into the IAC while the engine is running so the more you can keep it at ldle, the more cleaner you can get to the IAC. The engine will die when enough cleaner gets into the IAC to block off air flow but that's ok, the more that gets in there the more it can "cook" and loosen the crud that forms inside where the IAC is controlling the air flow.

It's actually easier to just remove the IAC and clean its plunger and the hole in the throttle body the plunger fits into, it is only held onto the throttle body with two small torx screws, T-25 I think.

That plunger is solenoid controlled so it moves in/out under the computer's control to control how much air it lets into the engine at idle RPMs. Cleaning its plunger and the hole in the throttle body it fits into will typically restore it back to 100% operation.

Finally, the engine gets its air via the throttle body via either the big round butterfly valve that opens when you step on the gas, or from the Idle Air Control Passage Inlet slot just above the butterfly valve. When the butterfly valve is closed, as it is at idle RPMs, then it must get air via the IAC... which if it's dirty, the engine won't run or won't run well at idle RPMs. Hope that helps.
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Old 10-25-2012, 04:05 PM   #7
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So good news! Went and got some cleaner and just went ahead and took off the whole throttle body and cleaned it and the iac plug. Now it idles great at stops. Thanks for the input!

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