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Old 08-11-2012, 04:46 PM   #1
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TJ Dying When Idling

I have a 2003 Wrangler Rubicon with automatic transmission I bought about a month ago. Its my first Jeep. I have a random issue that only happens while in gear(drive or reverse, happens more often in reverse and never when in park) the Jeep will idle low, the engine will rev itself and the rpms will bounce up and down between revs until it dies after 3-4 bounces.

I can't recreate it every time so it seems random. It never dies when up to speed but only at low speeds like when in reverse. It has 98k but the engine was replaced by the previous owner at 92k with a Jasper engine. It also has a new fuel pump.

I put some Seafoam in the gas tank hoping that fixes/helps the issue but haven't ran it all the way through yet. Any other ideas on what is happening? Thanks in advance.

First post by the way. Glad to be part of the forum.

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Old 08-11-2012, 05:00 PM   #2
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I forgot to mention that when doing the key dance trick I get no codes.

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Old 08-11-2012, 05:45 PM   #3
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sounds like an air flow problem. could be bad air filter or mass air flow sensor.try new air filter and plugs. clean throttle body with spray cleaner.
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Old 08-11-2012, 05:56 PM   #4
Knows a couple things...

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An engine's inability to idle that runs ok when you step the gas pedal generally always means the IAC (idle air control) is dirty and sticking. The IAC is what provides all of the engine's air when you are not stepping on the gas pedal, it provides an alternate source of air for the engine during those times when the butterfly valve on top of the throttle body is closed from not stepping on the gas pedal.

Cleaning the IAC can sometimes be done well enough to clear the problem by cleaning the throttle body's interior with an aerosol throttle body (not carburetor) cleaner. Read the directions on the can for how to do it. There is an 'idle air contro passage inlet' slot machined into the throttle body, see below, that is the air source for the IAC which sucks its air through that slot. Though this will tend to kill the engine when doing so, be sure to direct some of the spray towards the air passage inlet slot so the cleaner can be sucked in and work on the IAC.

If that doesn't do it, remove the IAC and clean its solenoid actuated plunger with throttle body cleaner and a toothbrush. Clean the hole in the throttle body the plunger fits into with throttle body cleaner and a baby bottle nipple brush or similar.

No need to replace the IAC, cleaning it will restore it to proper operation and restore your engine's ability to idle.
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Old 08-13-2012, 06:09 PM   #5
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Thanks for the ideas. I will have to try that next weekend.
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Old 08-13-2012, 08:31 PM   #6
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I just fixed my idle problem, and i had two similar issues. #1 After engine swap i lost some tranny fluid, replaced it and checked in park, seemed ok , but every time i went from reverse to drive it would stall, so of course i went to forum and found out it needs to be in neutral , and i was two courts low, and that took care of that problem, no more stalling. #2 check your grounds, since you just had a swap done also, it could be that, mine was very loose at firewall and my idle was very low and sputtered, fixed that ground now idles smooth. BTW i changed my iac and tps and it did not help, but i would suggest doing what jerry said and then check those two issues i mentioned. good luck
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Old 08-18-2012, 03:32 PM   #7
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Cleaned the throttle body and IAC today. It was very dirty in the IAC. So far it has not died on me. Overall the engine is running better and has noticeably more pep.

I appreciate the help.
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Old 12-29-2013, 12:25 AM   #8
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I know this is an old thread but I wanted to publicly thank Jerry Bransford for the information because it solved my problem also. Its great to have people here to share, help us learn and save us $$$.

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