2018 Yukon Denali with the 6.2 and 91k miles. Check engine light came on with a code for a misfire on cylinder #2. Buddy is a mechanic and tried to isolate the problem. First swapped plug wires with cylinder next to it, misfire still occurred. Swapped plugs, still misfiring. Swapped injectors, still misfiring. Cleaned valves, still misfiring. Pulled valve cover and said it appears one of the valves is sticking. Thinks it could be a valve guide and recommended replacing the head. I don't want to just throw parts at it so took it to a GMC dealer for a second opinion. They said it was a bad injector, I approved the replacement. They just went for a test drive and still misfiring (buddy had already swapped injectors above). They're digging deeper. Any ideas?

aggiepaintrain said:

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Lifters, Camshaft

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This. Assuming it's paid off, or close to, get the repair done. Buy the DFM/AFM OBDII tool and hopefully never run into this again while driving the Yukon in to the dirt.

aggiepaintrain said:

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Lifters, Camshaft

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Religiously changed the oil myself with Mobil one. What a POS to lose a cam at only 91k miles.

BMach said:

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2018 Yukon Denali with the 6.2 and 91k miles. Check engine light came on with a code for a misfire on cylinder #2. Buddy is a mechanic and tried to isolate the problem. First swapped plug wires with cylinder next to it, misfire still occurred. Swapped plugs, still misfiring. Swapped injectors, still misfiring. Cleaned valves, still misfiring. Pulled valve cover and said it appears one of the valves is sticking. Thinks it could be a valve guide and recommended replacing the head. I don't want to just throw parts at it so took it to a GMC dealer for a second opinion. They said it was a bad injector, I approved the replacement. They just went for a test drive and still misfiring (buddy had already swapped injectors above). They're digging deeper. Any ideas?

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Valves don't stick.

That is either a broken valve spring ( somewhat common) or a lifter failure.

Silvy said:

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I'd say lifter failure is significantly more common than a broken valve spring.

With a proper repair, you won't need to rely on software to prevent this again. Replace hardware (lifters & cam) to disable AFM

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What is AFM

P.H. Dexippus said:

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"Active Fuel Management" = cylinder deactivation to boost mpg

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Ah gotcha

I am surprised nobody has brought up the ignition coil - that's probably the #1 misfire root cause.

Bonfire97 said:

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I am surprised nobody has brought up the ignition coil - that's probably the #1 misfire root cause.

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Here's to hoping that's it and not the cam!

Bonfire97 said:

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I am surprised nobody has brought up the ignition coil - that's probably the #1 misfire root cause.

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OP needs to clarify if the bad code follows the respective coil... or, after the coil has been swapped does the code remain at the suspect cylinder.

If the code is following the coil then, yes... replace the coil.

JamesPShelley said:

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Bonfire97 said:

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I am surprised nobody has brought up the ignition coil - that's probably the #1 misfire root cause.

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OP needs to clarify if the bad code follows the respective coil... or, after the coil has been swapped does the code remain at the suspect cylinder.

If the code is following the coil then, yes... replace the coil.

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Code remains at the same cylinder

Any updates?

fixer said:

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Any updates?

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None yet, called the dealership on Friday and left a voicemail but never heard back.

fixer said:

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Any updates?

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Dealer called today to get authorization to remove the head and scope the cam…fuuuuck

Damn it!


Was there any audible clues of a bad lifter like a loud ticking noise that got worse with rpm?

Dealer finally got back to me. Pitted cam shaft, not worn off lobe. Doesn't matter, cam still has to be replaced. Estimate is $14k…

Silvy said:

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Get your 7 year old vehicle out of the dealer and to an independent shop.

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Yeah, that's where it's going.