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Old 11-20-2019, 02:08 PM
Thread Starter
Join Date: Jun 2018
Posts: 59
TJ straight 6 wont idle

Replaced the spark plugs and bolted the rail back up and now I can crank up and it will idle at about 900RPM. However as soon as I pull it into gear, it drops 500 RPM and wont stay running.I can keep it running by keeping my foot on the accelerator but just want to get it right.

FYI: it is an automatic. Iím thinking that maybe Iíve bumped something or bumped a plug gap or maybe the rail isnít making good contact with a plug or something but why will it idle until I put it in gear?

Thanks guys!

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Old 11-20-2019, 02:30 PM   #2
Join Date: Jan 2019
Location: Round Rock, TX
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Do you have any codes or check engine light? Did you bump a fuel injector connector off? Double check your the ignition coil rail plug.

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Old 11-20-2019, 03:44 PM   #3
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On wifeís 04 rubi 5 spd after a low of disconnected battery have to drive it 20-30 minutes to let it relearn idle before a foot off gas does not make engine die

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Old 11-20-2019, 04:14 PM   #4
Knows a couple things...

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Location: Escondido, Calif.
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Check that you didn't bump the connection to the IAC (idle air control) located on the same side of the throttle body the coil rail is located on. I'd disconnect that connector and then reseat it to make sure it has a good connection to the IAC.

A couple more things that can cause a low idle is a nearly dead battery (yes) and a dirty IAC which can be cleaned with throttle body cleaner sprayed into the throttle body while the engine is idling. Keep the engine at idle to insure the cleaner passes through the IAC to clean it. Raising the rpms off idle will cause the cleaner to bypass the IAC. When the engine dies from spraying cleaner into the TB, that's normal. Just let it set several seconds to let the cleaner work then start the engine again and spray it again.
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Old 11-20-2019, 04:25 PM   #5
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You didn't say what year or what engine...
That would be a HUGE help.

But, what I can help with is some basic trouble shooting. Since the problem presented directly after you preformed work, that is where you should start. Go back through and make sure you did everything correctly. It's highly probable that you introduced the problem, however it's a Jeep---sometimes more than one thing breaks at a time and it will have you chasing your tail until you figure it out. Jeeps think it's funny to tease their owners and pull shit like that!

Here is where I'd start.

First give us all of the deets on your Jeep (year, engine, trans, mods, etc.) I do see you said you have the 4.0 I6. 97,98 have a traditional cap and rotor where 99-06 have a coil pack.


If you have a coil pack that mounts directly over the plugs, make sure that you have each plug fully seated in the boot, you should get a slight "click" when the plug mates completely with the connector inside the boot.

If you have plug wires--again make sure that each boot is fully seated on the plug and make sure that you haven't crossed up any of the wires.
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Old 11-21-2019, 07:13 AM
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Join Date: Jun 2018
Posts: 59
Sorry, Our TJ is a 2000 Sahara automatic with a straight 6 engine👍🏼

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