My 08 6 speed (aFe CAI & Catback) started pinging about a month ago. I put some octane boost in the tank and it took it away after that I started filling up with 91 and had no issues. The last week or so I have noticed it faintly pinging running on 91. I decided to fill up with 87 and try to eliminate the pinging. First I tried plugs and wires.... Still pinging than I tried seafoam down the brake booster line ..... Seem to have noticed some difference but still pinging. My next guess is bad knock sensor or dirty injectors. Any help will be appreciated. Also the jeep is not throwing any codes.

 

Assuming you are not lugging the engine...

Could be carbon build-up in the combustion chamber. Are you having any oil burning issues?

 

Not lugging the engine.... I burn half a quart between oil changes.

 

What brand gas? Try running a bottle of Chevron Techron in a full tank and see if it improves...

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Check your pcv valve. More than likely it is gunked up and needs replaced. How do you drive it? Short frequent trips can cause carbon build up. Take it on the interstate and get on it. Drive it for a while at higher rpms to blow out carbon buildup and see if that helps

 

Changed Pcv recently. I don't baby it I do mostly highway and road trip with it fairly often. After I did the sea foam I went for an hour drive on the highway and kept the revs between 3-4 grand. It helped but far from cured.

 

What oil do you run?

 

Mopar 5w20

 

Things I have played with:
Switch to 5w-30 mobil 1
New PCV valve
Cleaner
One heat range colder plugs - this seemed to do the most good for me, no fouling problems at all. I used NGK Iridium plugs "6" heat range. LZT6AIX-13 IIRC it is what a bunch of the Hemi guys run.

This solved it for me. I did not get around to changing the knock sensor.

 

So the knocking is gone completely?