2012 JKU engine stumbles randomly - JKowners.com : Jeep Wrangler JK Forum
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post #1 of 12 Old 11-21-2019, 04:18 PM Thread Starter
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Lightbulb 2012 JKU engine stumbles randomly

Ok, I have an issue that has me stumped as to the cause. My JKU will randomly stumble when I am driving. When it stumbles I lose about 2-300 rpm for a second or to then everything is fine. It is truly random as it occurs driving in town or the intestate and may occur once or a couple to times as I am going down the road. I have scanned it and there are no engine codes and no transmission codes. Any thoughts as to where to begin to look would be appreciated.
Thanks
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post #2 of 12 Old 11-21-2019, 04:39 PM
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Mileage/recent maintenance etc? Auto/manual?....

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post #3 of 12 Old 11-21-2019, 07:29 PM
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cracked exhaust manifold.


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post #4 of 12 Old 11-22-2019, 09:13 AM
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Originally Posted by j3ff3ry_j33p View Post
cracked exhaust manifold.
3.6L exhaust manifold is built into the head.

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post #5 of 12 Old 11-22-2019, 01:21 PM
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Quote:
Originally Posted by peanut74 View Post
Ok, I have an issue that has me stumped as to the cause. My JKU will randomly stumble when I am driving. When it stumbles I lose about 2-300 rpm for a second or to then everything is fine. It is truly random as it occurs driving in town or the intestate and may occur once or a couple to times as I am going down the road. I have scanned it and there are no engine codes and no transmission codes. Any thoughts as to where to begin to look would be appreciated.
Thanks
Do any dash lights flash or flicker when this happens?

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post #6 of 12 Old 11-23-2019, 06:18 AM
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3.6L exhaust manifold is built into the head.

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drat

someday I will pay heed to the freakin' subject ...ugh ( mod-fail)


thnx for settin me straight ; my bad, OP.
'missed 'itsa Pentastar
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post #7 of 12 Old 11-23-2019, 10:24 AM
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how many miles?

two things to try:

1) clean the throttle body.

2) change the spark plugs.


2012s were susceptible to the valve seats coming loose and needing the driver's side head replaced. I think you need to throw misfire codes for more than one cylinder in that bank to qualify according to the TSB I saw a long time back now. You can check the julian date code stamped above the exhaust port on the head.
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post #8 of 12 Old 11-26-2019, 03:00 PM Thread Starter
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Thanks for the input gents. Let me give you more details as asked above:
-Jeeps Specs
Engine: 3.6L with no mods
Transmission: 5 speed automatic (W5A580). I did change the filter and fluid. Level is ok
Transfer case: command Trac Shift-on-the-Fly
Axles: front Dana 30 rear Dana 44 both have 3.21 axle ratio
Tires: 33"
Mileage: 82,000
I do have a 2-1/2" lift on the jeep.

I did use a AEV Procal module to turn off the low tire pressure warning chime and adjust the speedometer for the taller tires.

As for any warning lights when it happens no lights flash. Per the dashboard everything is fine when it happens.
I'll try cleaning the throttle body and see if that helps.
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post #9 of 12 Old 11-26-2019, 07:20 PM
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Crankshaft position sensor... https://youtu.be/BTiuxhwcp_I
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post #10 of 12 Old 11-26-2019, 11:03 PM
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My 2008 that I had did that because of leaky spark plug wires....they looked fine to me But on pros advice after it being on his high dollar diagnostic machine I put on a new set of wires and it ran just fine after that.
The ignition systems on these Jeeps must be one hell of a high voltage set up. He said they leak through the spark-plug boots after they get older. On another note the original battery in my 2014 wrangler died today and a $130.00 later I'm back in the running again, doggone batteries are not cheap for the good ones.

I thought getting old would take longer.
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post #11 of 12 Old 11-27-2019, 07:43 AM
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drinking water before bed

nice post`
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post #12 of 12 Old 11-27-2019, 11:57 AM
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Second on the sensor, it caused a few shutdowns for my 2012 JKU and it's only around $15
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