2020 6.2L: misfires, lifter issues and engine replacement

[B-train]

bad news - i changed the oil + seafoam out for plain oil and it went right back to misfiring after the change.

does this allow me to infer anything, e.g. that it is indeed a stuck lifter and not a broken valve spring?

Did they find anything other than gunk when they pulled the valve covers? A broken spring or bent pushrod should've been easy to see. But, being that you said it drove correctly before the oil change means you're on the right path. Add some more seafoam with your fresh oil and filter change and run it some more. I'd probably put on several hundred miles this go around with some good higher rpm pulls when it's not making any noise.

It's frustrating, belive me (daughter's nightmare lifter). It took some time and finessing, but it's been quiet as a mouse now for many miles. I will say that once a lifter gets gunked up, they are more prone to relapses with dirty oil. You got this man! Show it who's boss.....gently at first of course.

 

[persistent]

i will give the seafoam another shot. i've got an extractor, so i'll just pull a bit of oil via the dip stick tube and add in the seafoam.

do you recommend the same amount (1/2 qt) as before?

i'm leaning towards doing the dod delete mod myself at some point in the near future. nearer if i can't get this lifter unstuck.

according to the dealership, the misfires are on cylinder 8, and iirc that is a normal lifter and not a dod one.

 

[B-train]

i will give the seafoam another shot. i've got an extractor, so i'll just pull a bit of oil via the dip stick tube and add in the seafoam.

do you recommend the same amount (1/2 qt) as before?

i'm leaning towards doing the dod delete mod myself at some point in the near future. nearer if i can't get this lifter unstuck.

according to the dealership, the misfires are on cylinder 8, and iirc that is a normal lifter and not a dod one.

Yep, keep with the same program. It took many miles to gunk it up, so it's gonna take a bit to clean it out. Longer runs of highway speeds are best once you get it to quiet down.