Yes it did it one time before. About 90,000 miles on the buick

The old plug shots look a little hot, were they all like that? Im thinking vacuum leak if its more than 1 cylinder and its a lean condition

Picture of all 6 plugs

is this by chance a direct-injected vehicle , not a port fuel?

Yes it'* a direct injected

I have a feeling we are looking at the result of the direct injection switch from port fuel where the intake valves don’t get cleaned by fuel all the time so they gum up. Does this car have serviceable PCV and EGr components?
if so, clean them best you can, catch can for PCv if you can, and do a chemical engine cleaner. Gm makes an expensive one in a bottle and it really does a good job.. you basically nearly stall out the engine with a blue liquid and let it soak and then redstart and spray more in and it cleans

but at some point it may just need to be pulled and the valves cleaned. It’* a huge flaw. B

but I could be wrong on this and I hope I am, but if you do what I said at least to clean and check vacuum lines and components, using a off the shelf engine top end cleaner like sea foam and then driving the car in sport mode(if it has it) and very aggressively up a steep, long on ramp a few times might help

this will at least buy you time

https://www.enclaveforum.net/threads...i-engine.9561/
got a 3.6? Intake manifold only has to come off the head stays on

The LLT doesn't have a huge carbon buildup issue, both in reports I've seen in the wild and in the one that I own.

More likely that it is a fuel pressure issue, maybe a flaky injector, or maybe a sensor giving bad (but legitimate looking) data to the PCM.

Have we checked the air filter yet?

never a bad idea. KISS. Any oil burning?

Air filter was changed recently too. I would have to add about half a quart every 2,000 miles. I ended up bringing the car to the mechanic today. I will let you guys know if he finds anything.