This video by GM is 5 years old, but I've never seen it discussed. Apparently low oil pressure is or can be the culprit. Low oil pressure caused by plugged VLOM filter, or VLOM leak causing a "miss timed" reactivation event of the lifter. Or IMO, using 0w20 oil, but that's just me.
GM AFM lifter failure mode identified by GM?
- Thread starter another Todd
- Start date
4WD
$50 site donor 2024
Well - so far all indications are my 2017 has a clean engine …
We‘ll see …
We‘ll see …
Not a GM guy so just my 2c.
Do all AFM failures cause by sludge motor/low oil? And if no oil pressure is an issue, using 0w20 would have helped as it's easier for oil pump to build up pressure?
Could switching to a higher output oil pump solve this issue?
I feel like if AFM switching from v8 to v4 under high rpm, the solenoid may get caught in between if not retracted fast enough, but ECM should know better and avoid this situation?
Anyway thanks for sharing. It's interesting to see how AFM works.
Do all AFM failures cause by sludge motor/low oil? And if no oil pressure is an issue, using 0w20 would have helped as it's easier for oil pump to build up pressure?
Could switching to a higher output oil pump solve this issue?
I feel like if AFM switching from v8 to v4 under high rpm, the solenoid may get caught in between if not retracted fast enough, but ECM should know better and avoid this situation?
Anyway thanks for sharing. It's interesting to see how AFM works.
Failures are not happening at startup, so I don't think building pressure quickly by the OP plays into it. The oil pump on mine and I think 2014 and up has a 2 stage feature (not sure how that works), my normal oil pressure below about 3600 RPM is around 35-40psi IIRC, above 3600 it jumps up to about 60psi IIRC. I don't remember what my hot idle OP is, but now I am going to check my pressures at all RPMs.
OVERKILL
$100 Site Donor 2021
It's not. Just like MDS, it only engages when the engine is in a state that's conducive to dropping out of V8 mode, which is typically steady state, low RPM cruising.
ls1mike
$50 Site Donor 2024
It is a variable displacement oil pump.
4WD
$50 site donor 2024
That’s what they call it - but I always see one extreme or the other on pressure - it maxes out based on demand (pedal) before the high RPM’s are even there (which makes sense to me) …
Always figured no middle ground as before …
ls1mike
$50 Site Donor 2024
Variable Displacement: The Future of the Oil Pump is Here – UnderhoodService
Variable displacement oil pumps control how hard the pump works by matching the pressure and volume to engine temperature, loads and engine speeds.
www.underhoodservice.com
The newer failures like in the 2021 and 2022 models were failing at 4k to 10k miles from new. It was an issue with a bad batch of lifters. But if you ask me, it is still the quality of the lifter. GM going with the lowest bidder and this is what you get. Even those that deactivate AFM/DFM are still having failures. Best to let it ride through warranty and if you plan on keeping it, either take a chance or completely remove the system all together.
