2012 Yukon XL Denali 6.2l

[Raynaa219]

I’m not sure if I’m posting this in the correct forum, but hoping someone can be of some help. All of a sudden when driving the stabiltrak and traction control turned off, CEL started flashing(accompanied by what seems to be a lifter tick) scanned and got p0301, changed all spark plugs and wires. Ran fine idling, then problem returned after driving maybe 2 miles. Switched the coil with cylinder 3, cleared codes, and problem returned, still with p0301. Pulled spark plug from 1 and 3. Plug from cylinder 1 has an excessive carbon build up(will attach pictures). From my understanding on start up, it’s firing on all 8 cylinders, so if it is a failed lifter due to the afm system, why wouldn’t it be ticking from start up, and what would cause it to start ticking but go away after shutting vehicle off and turning it back on? 

[swathdiver]

17 hours ago, Raynaa219 said:

I’m not sure if I’m posting this in the correct forum, but hoping someone can be of some help. All of a sudden when driving the stabiltrak and traction control turned off, CEL started flashing(accompanied by what seems to be a lifter tick) scanned and got p0301, changed all spark plugs and wires. Ran fine idling, then problem returned after driving maybe 2 miles. Switched the coil with cylinder 3, cleared codes, and problem returned, still with p0301. Pulled spark plug from 1 and 3. Plug from cylinder 1 has an excessive carbon build up(will attach pictures). From my understanding on start up, it’s firing on all 8 cylinders, so if it is a failed lifter due to the afm system, why wouldn’t it be ticking from start up, and what would cause it to start ticking but go away after shutting vehicle off and turning it back on? 

Probably is a failing de-ac lifter.  Get a Tech-2 on it for proper and more thorough diagnostics.  Unlikely, but an injector could also be a culprit.