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Discussion Starter #1
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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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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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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Discussion Starter #8
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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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.
 

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Discussion Starter #13
Well I waited so long I had another issue pop up. The thermostat housing burp screw was leaking antifreeze. So I removed the throttle body to get easier access to the plug. After putting on a new o-ring on the plug I cleaned up the throttle body. After reassembling everything took it for a test drive and same issue occurred.
So I can rule out the throttle body. I think the next best option is the crankshaft position sensor. I will let you know how that turns out.
 

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Well I waited so long I had another issue pop up. The thermostat housing burp screw was leaking antifreeze. So I removed the throttle body to get easier access to the plug. After putting on a new o-ring on the plug I cleaned up the throttle body. After reassembling everything took it for a test drive and same issue occurred.
So I can rule out the throttle body. I think the next best option is the crankshaft position sensor. I will let you know how that turns out.
I've been chasing a similar problem. Like you, I cleaned the throttle body to no avail. I have been documenting my issues carefully to define a pattern (if possible), in the event I need to take my Jeep to shop for further diagnosis.

I had also read about a faulty CPS being a possible cause of this problem. In fact, in re-watching the youtube video (above in a previous post of this thread), I saw where he noted that his traction control light illuminated at one point. Just this morning, I experienced the hesitation. At the same time, the traction control light illuminated. I was gently accelerating on completely dry ground, with no wheel spin or slippage. As soon as the hesitation end, the traction control light went back off.

I plan on also changing the CPS, hopefully in the next few days.
 

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Discussion Starter #15
I replaced the crankshaft position senor and my issue has been solved. I wanted to run it for a month or so to make sure the issue did not come back. Thanks for all the help in figuring it out:grin2::grin2:
 
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