2020 6.2L: misfires, lifter issues and engine replacement

B-train · Nov 20, 2024

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 · Nov 22, 2024

B-train said:
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 · Nov 22, 2024

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 · Nov 23, 2024

Any luck with the weekend warrior lifter battle?

persistent · Nov 25, 2024

B-train said:
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 · Nov 25, 2024

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 · Nov 25, 2024

persistent said:
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 · Nov 25, 2024

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 · Nov 26, 2024

B-train said:
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 · Nov 26, 2024

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?

2020 6.2L: misfires, lifter issues and engine replacement

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