2020 6.2L: misfires, lifter issues and engine replacement - SOLVED

[B-train]

At this point, your cheaper options may work out the best due to the timeline. IF the engine is shot, you won't be doing any more damage than what's been done.

Also, check out car-part.com as an option. They have a whole network of auto recyclers where you can get anything you need. Then find an independent shop with a good reputation and see if they will do an engine swap.

 

[persistent]

Listen to @the 18th letter this is a good, cheap, option. Aka: the Tennessee Tune-up as well. LOL

1. Change the oil and filter
2. Add approximately 1/2 quuart of Sea Foam, MMO, or ATF (Ratio is on the cans of Seafoam and MMO).
3. Let engine idle with new mixture until it gets warm
4. Run in neutral at rpms of about 1200 to 1800 (think massaging the mixture into the system)
5. Take the truck out and do some moderate pulls through the gears (not WOT).
6. Listen to the motor - is it quieter or noisier?
7. If it seems like improvement is being made, then give it some more rpm and longer pulls. Then coast for a bit and let the decell cycle pull oil up and around under vacuum.
8. Make a long run to Costco on the freeway. Buy more oil and filters
9. Let truck cool and sit overnight. Fire up in the morning and see if noise is gone. If gone, change oil and filter. If still slightly present, repeat the process and change the oil hot afterwards.
10. STOP using 0w-20 and go with 5w-30 Dexos.

This may or may not fix it depending on how bad the lifter issue is, but I'd be willing to bet it will work.

As far as the engine price, that's a major amount of suck, but seems common in this market. An independent shop may be a better option. They can still put in new GM engines with the warranty as well. 3yr/100k miles - done many over the years as an independent

should have car back tomorrow, and i am planning on running compression and leakdown tests and having a look under valve covers to localize the problem.

with that in mind, i have a few detail questions re your advice.

2 - am i right to assume that i should leave some space for the sea foam, versus adding SF after the oil is topped up? example - leave 1/2 qt of space below max oil fill on dip stick.
9 - if i'm seeing improvement in the sounds from the engine but not a total recovery, repeat the driving until it recovers?
10 - what's the motivation for switching from 0w20 to 5w30 dexos? i have a decent amount of 0w20 on hand, thus the question.

i am planning to do what you suggest first, before doing the testing.

 

[B-train]

2 - yes leave some space. There is a ratio on the can for how much to add with engine oil. I added 1/2 can to my 2017 when I thought I had a lifter issue. I only put 8 qts of oil in at oil change, capacity is 8.5qts (GM revised the quantity if I recall correctly).
9 - yes. With lifter noise if it starts lessening to the point of almost gone, then drive it some more with higher rpm pulls (this ups the oil pressure and volume). Don't be surprised if it's quiet and then noisy the next day after a cool down cycle - it's happened to me a number of times on a 3800 in a buick that was neglected before I got it for my daughter.
10- 0w-20 vs 5w-30 is a preference for myself (and others) due to the fact it is still a somewhat robust oil that is used in GM commercial vehicles (read: CAFE exempt). 0w-20 is a gimmick that GM uses to gain a fraction of a mpg for cold starts to boost their overall CAFE rating. I personally don't think it's worth running something that thin in an engine designed to do work and move a lot of weight on a regular basis. I get your wanting to use it up though. Just use it and see where you're at when it's gone.

If you want a phone convo to help out, PM me and we can chat.

 

[B-train]

Any luck with the weekend warrior lifter battle?

 

[persistent]

Any luck with the weekend warrior lifter battle?

the wife didn't want to get the car on friday or saturday, so i got it today.

changing oil and filter rn, will report after doing the break in procedure you recommended.

 

[persistent]

the car is driving more or less how it used to immediately after the oil and filter change, with the check engine light having not come back on (yet). qualitatively, the engine is no longer vibrating / shuddering the way it was when i drove it home from the dealership. however, i did use my scan tool, saw a generic misfire dtc (P0300), cleared all dtcs, scanned it again, and saw the misfire dtc again. i have driven the car about 20 mi since the change, being mindful to push it a bit further as i drive it. i will take it for a drive on the highway tonight.

EDIT: can anyone tell me of a scan tool that gives realtime per-cylinder misfire data? this launch x431 i have does not seem to be able to give realtime misfire counts, much less per cylinder.

 

[B-train]

the car is driving more or less how it used to immediately after the oil and filter change, with the check engine light having not come back on (yet). qualitatively, the engine is no longer vibrating / shuddering the way it was when i drove it home from the dealership. however, i did use my scan tool, saw a generic misfire dtc (P0300), cleared all dtcs, scanned it again, and saw the misfire dtc again. i have driven the car about 20 mi since the change, being mindful to push it a bit further as i drive it. i will take it for a drive on the highway tonight.

EDIT: can anyone tell me of a scan tool that gives realtime per-cylinder misfire data? this launch x431 i have does not seem to be able to give realtime misfire counts, much less per cylinder.

I don't know of anything other then GM stuff. HP tuners has real time logging and graphing, but that's a whole nother ball of wax.

Have you been driving it with Seafoam, or equivalent, in the engine with the fresh oil?

 

[Fless]

Torque Pro by Ian Hawkins ($5 on Google Play) has extended GM PIDs for individual cylinder misfires, see attached. Combine that with a quality OBD device like the OBDLink MX+ and you should be able to see them using that.

 

[persistent]

I don't know of anything other then GM stuff. HP tuners has real time logging and graphing, but that's a whole nother ball of wax.

Have you been driving it with Seafoam, or equivalent, in the engine with the fresh oil?

yep, running with fresh oil and filter with 1/2 qt seafoam, per your recommendation. qualitatively, the check engine light has remained off and the car idles and drives like it did before the problem started. i will be changing the oil and filter again a bit later today.

iirc, MDI2 is the GM oem diagnostic tool, and it requires a paid subscription and internet access, which is a dealbreaker for me. i don't need diagnostic info very often, so paying for a subscription doesn't make sense, beyond the surveillance component.

 

[persistent]

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?

 

[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.

 

[persistent]

another round of 1/2 qt seafoam got the lifter unstuck again, and after 400-500 mi without it sticking again, it's throwing CEL again.

i will try another round of seafoam shortly.

 

[persistent]

as a result of these lifter problems, i decided to do a dod delete myself, which would give me an opportunity to observe and clean the top of the engine.

after taking off the lifter covers, i found no visible sludge. could it be cleaner? sure, but no sludge.

i will cut open my 2 filters from the seafoam runs and post pics of head tops soon.

 

[fr8bil]

K&N.

i was just going off the packaging that said they were good for 20k mi. if the service interval should be every oil change, that's easy enough to adapt to in the future.

i'm really surprised at the amount of crap i'm catching for not changing the filter more often. my recollection of every car i've ever taken to a dealership is that they definitely would not change the filter every time the oil was changed. telling me i'm an idiot for not changing the filter more often does literally nothing to help me make a decision about the repair.

OK, oil filter aside, yes, take the vehicle to an independent but trustworthy, shop ( if you can find one) and have them pull the cam and inspect the lobe that the stuck lifter rides on first. Maybe you can get your problem solved with just a new bump stick if the stuck lifter ground down the lobe, and maybe not, but you also need to run some engine flush a lot stronger than good old Sea Foam through the existing engine and do at least three low-interval oil and filter changes. A decent reman engine with a warranty from someone like Jasper shouldn't set you back $14K parts and labor ( I could be wrong with the damn inflation but it's worth shopping around ) if the cam/lifter replacements fail. Seeing the date of your last reply I'd assume you have addressed the issue by now so overlook the nasty replies you got and fill us in on your progress please.

 

[MrMonte]

Highly recommend installing a non AFM cam & lifters.

I did the AFM delete on my 2018 Yukon Denali 30K miles ago. Took me 20hrs to complete. I didn't pull the engine or drop the oil pan. I did a thread on cam swap.

 

[peteytahoe]

I have a 2020 tahoe 6.2 and put a whipple supercharger on at 4000 miles.. had a misfire in 6 months.. installer went through it put new plugs couldnt find it.. i found it was a ignition coil and changed myself

 

[persistent]

UPDATE: i replaced a lot of stuff in the top of the engine, but that didn't fix the problem. ends up it was failed piston rings on cylinder 8. the engine now idles fine with no misfires.

this is a reminder that you should always do a compression and leakdown test yourself before disassembling the engine.

 

[tooleyondeck]

Thanks for the update and advice on testing compression first. A year of dealing with that issue is a long lesson to learn.