So i would get this rattle noise when the engine was under load from 2k-3500rpms mostly on uphills. I always thought it was the heat shield and i took my jeep into the dealer twice and they said it wasn't the heat shield and that the noise was "normal". Well after a year or so I decided to put in higher octane gas today and FIXED!! I bought this 2011 jk with the 3.8 engine used with 7k miles and the dealer said 87 octane is what i should be using, so thats what i did. Now i am wondering if maybe my jeep has a chip of some kind of aftermarket tune. Anyways i am happy to figure this out.

 

I had the same issue in my 2011. Chased a rattle for a few weeks checking heat shields, driveshafts, exhaust, etc and was going nuts. The rattle only happened under load. Gassed up with premium one day and suddenly no rattle. Now that I know it was caused by the gas I realized the worst rattle I was getting was when I used 87 octane costco gas. I don't get gas at Costco any more. (I have a superchips tune installed in mine and was running their 87 octane tune, btw)

 

You may want to look into having the engine decarbonized - it could have carbon build-up, which leads to higher compression and premature detonation. My 2010 JK runs fine on Costco gas.

 

Is this something i should leave alone and keep putting higher octane gas or should i worry that it is making that rattle noise on lower octane?

 

Some 3.8s ping with the recommended 87 octane gas. In Denver 89 is the highest octane available and mine still pings a bit. I tried the Mopar combustion cleaner twice with no luck. Only does it on warm days and under load when driving up hills.

 

The first thing I would do is try a carbon treatment on the motor. Mopar CCC through the throttle body and seafoam in the tank. Be sure to let the CCC soak for longer than is recommended on the can, drive it kind of hard afterwards and change the oil. Also, this tends to be more of an issue with the oil burning motors. Running higher octane gas is only a bandaid to the detonation problem, and running tuners tends to make itbeven worse.

 

How do you apply the Mopar CCC? Just spray it in the throttle body when your cleaning it, I watched a you tube video and guy had the engine running. How did you apply it?

 

Yeah, spray it directly into the throttle body. It works best to have 2 people. One spraying the can, and the other in the vehicle to keep the engine running, as it will want to die. I think the most important thing is to give the product plenty of time to soak and break up the carbon deposits.

 

I had this issue as well. I was running the superchips programmer and a afe stage 2 intake. Ping under load on hills. Changed my plugs and it seemed to removed it 95%.

Put on my supercharger and the jeep still knocked until i got a proper tune done.

Removed the blower, running 5-30 oil, aev gen2 snorkel, stock airbox with dryflow filter and mbrp exhaust. Jeep runs like a champ. No knock or hiccups at all. You should try new plugs. My ngk platinums have been awesome.

 

I did not have that issue when I did the CCC myself. The can actually tells you to kill the motor by suffocation (which mine wouldn't do).

Additionally I've run seafoam in the gas and there's no reason to change the oil after that. Same deal with the CCC as it doesn't touch the oil (unless you've got poor seals).