Hello, I purchased a 2012 JKU 3.6 6 speed today. It has an issue which is why I got it cheap, maybe you guys can point me in the right direction. I purchased it as a “project” with this known issue. Allegedly spark plugs, coils, cam and crank and o2 sensors were all replaced.
It cranks right up and sounds find while at high idle. However once it idles down it has a random misfire that I’m told is coming from the passenger side. I’m also told it will stall out if run for more then a few minutes (have not run it long enough to experience that). The misfire Is random so I’m more prone to think its timing chain related, then head or cams which probably would be limited to one cyl. What are y’all thoughts and where should I start looking ? The rig only has 54,000 miles on her. Thanks !!

update she smokes like a banshee, it’s a light grey smoke not a think white smoke. Drove it around the block and she does not want to rev much past 3500 rpm.

 

You should do a compression check on all cylinders. I bet the one that's misfiring has low compression. If that's the case the spark plug will also be fouled on that cylinder.

 

More then likely the wiring at the right cylinder head cam sensor is bad, i bet if you unplug this connector (center rear of valve cover) and tug on each of the 3 wires you will find one that is broke internally in the insulation. Replace connector and add some length to wiring so its not so tight in harness, clear codes and test drive. If that isnt it you could have a bad phaser on camshaft.. Make sure there is no sludge in engine, and only use high quality oil and filter.