Hey guys. I had this (unfortunately not uncommon) Pentastar engine happening in the end of last year and thought I post my experiences for everyone who comes across the same issue.
What has happened
Throughout the last two to three months of last year my Wrangler JK with the 3.6L Pentastar engine has developed a metallic engine ticking noise which in the end was very noticeable. The first time I noticed that ticking noise was during a traffic jam when I was standing next to a concrete divider with the side window open. This little concrete wall had reflected the engine noise and I started to hear a little metallic ticking.
I didn't think much about it at that time but over the next couple of weeks it would become more noticeable. It started to make me worried when I could hear loud mechanical ticking whenever I entered or left my lock-up garage or passed a big truck which also would reflect the engine noises back into my car's cabin.
Besides the ticking noise there were no other symptoms. Fuel usage, power and smoothness of the engine stayed the same which was kind of a relief as if any of those issues had turned up then underlying issues could have been more serious.
Diagnosis of the Engine ticking
The ticking would become faster with increasing engine revolutions and slower when getting off the loud pedal. I tried different grades of fuel (E10, 95, 98) and injector cleaners to rule out any fuel issues or carbon build-up. Obviously this did not change anything. I recorded some videos from under the bonnet (will upload shortly) trying to locate where the ticking noise is coming from and tried to rule out any loose parts in the engine bay. I heard for example that some heat-shields could become somewhat flexible and produce similar ticking noises caused by engine vibrations.
After taking a bit more time with the my human radars (aka ears) I pretty much tracked the noise down to the driver's side engine head. I googled the symptoms and found a few owners reporting that the roller rocker arms were worn - or to be more specific, the bearings within those arms had somewhat collapsed. One user had stated that Chrysler had used the wrong grade of steel for the pins in those bearings which then wear down the center axle of the bearings.
Well, I didn't fix it myself to be honest but at least I tracked down the cause and ordered the parts. I found a shop on ebay selling genuine sets (Chrysler/Mopar) of Roller Rocker Arms and Hydraulic Lash Adjusters for about 77 USD (including shipping) which arrived here within a week. I talked to several mechanics (some wouldn't even touch the Jeep which I found silly as it's an engine that has been used in many other cars too and if I have had the time I would have done it myself). Luckily I found a mechanic who was willing to do the job after an initial diagnosis (he approved of my theory).
Unfortunately the driver's side head of the Pentastar engine is a bit of a pita and it took him a lot of time to disassemble and re-assemble the manifold to get to the actual cam-shafts to replace the rocker arms (which itself was an easy job). It's about half a day's work and shortly I got my Jeep back all quiet again. :)