It is easy to tell spark knock and exhaust leak differences. They don't sound anything alike...

 

i installed a banks cat back system last fall, but my problems started before that. with the doors off i can smell some fumes that i know are my jeep, because im alone..just noticed the last two days with no doors. hmmmm

 

Okay I have a 08 with 17k miles and have the ping issue. It only happens when the engine is a full temp but mine is not just slight a ping. It sounds like a 79 Pinto running diesel fuel. I get the ping around 1500-2000 rpm and when underload. I have had it in the shop 3 times in the last two weeks and its getting noticably worse. You can hear the valves just banging away like there is marbles in the intake. The dealer definitely knows it is not normal or a "JK thing" so please people dont fall for that stealership bullshit. Valve knock is not normal and will severaly damage the engine overtime. I did get the "its bad gas" bullshit line from them the first time but I only use quality gas and was actually running 91 at the time to try to lesson the noise.
So far they have replaced all the valve lifters and de-carbonized the entire engine ( this should not be necassary with 17k miles ) and also reflased the Ecu. Still the same issue. They are now waiting to hear back from Detroit for the next step. Personally I think the valve guides on the 3.8 are complete shit. The valves are most likely vibrating when the engine warms up and the quides expand causing the noise and the oil disappearence ( 1 qt per 1000 miles which started at the same time as the ping). I dunno Im strongly thinking of putting 10/30w in the engine but the dealership is still continuing to address the problem thank god.

 

I heard the pinging again today ughhhhhhhhhh

 

Don't blame E10 gas for ping issues, it burns cleaner and leaves less carbon behind only helping the situation. Many tuned out turbo and supercharged folks actually run E85 for it's resistance to pinging. It's like cheap race gas.

Assuming the pinging happens once fully warmed up there are several things to check. Scan engine to verify both banks are using same amount of fuel, check amount of knock retard in realtime under load, verify TC lockup at proper speed/load, check for clogged cat.

Pinging is typically a load based event, when it happens shift into the next lower gear to stop it until you can get it diagnosed or fixed.

I'd be visiting the dealer regularly until fixed. I would offer to pick up the service manager on an empty tank, ask them where they buy their fuel, fill up in front of him and then duplicate it for him. Do it on a hot day.

 

Why wouldn't I blame the Bio-fuel shit? So then explain why my pinging quits when I use 89 or higher Octane?? Then when I fill it up at other stations with 87 and the pump states it may contain 10% bio-fuel it starts pinging again? Thus I believe it's a combo of shitty 87 Octane bio-fuel blend and a faulty knock sensor in my case.

 

I have an 08 and pull a trailer with no pinging issues, and I run whatever 87 I get

 

RevyJK - It's unfortunate you have this problem, but honestly I have tried every grade of unleaded, with and without ethanol blended in, and it makes NO difference. I have a 2009 X w/ manual, running the 89 octane Superchips tune. I can still run any type of 87 octane gas (or higher) without a problem. I run 315/70-17 tires with 3.73 final drive.
It ain't the gas friend. The knock sensor, maybe.

 

That may be dirt. But the dirt has to have something to stick to. And mine was slightly knocking too. I was running 87 octane. I switched to 93 octane. And I have not had it knock in over a year.

 

next time you fill up, check the E rating, I was traveiling last month and one of the stations I pulled into had E15, not E10.

15% ethanol? that would hurt octane at 87 and you would have to run higher octane just to get back to 87 levels.