2022 / 2023 GM V8 AFM Question

[Wylie6G72]

Hi Everyone.,

I did a lot of digging today, here and on the net, about the status of GM's AFM

Is this system still causing issues with the engines? I find lots of remarks about older pickups, Tahoes, etc. but nothing very current.

 

[CKN]

The New Ones use DFM. Not AFM. Started in 2019. There were lifter problems earlier on-which was a supplier issue and not a DFM issue. Thus far it seems less problematic than AFM.

It's very common to see new trucks which have been shipped without his feature activated-due to the chip shortage. But the internals are still there.

https://gmauthority.com/blog/2018/03/how-general-motors-dynamic-fuel-management-works-video/

 

[JavierH19]

My 2021 escalade has dfm but it may be deactivated but I'm not sure. When i drive i don't notice any change in engine operation characteristics. So it may be deactivated but dfm is also supposed to be almost undetectable in operation compared to afm.

 

[CKN]

My 2021 escalade has dfm but it may be deactivated but I'm not sure. When i drive i don't notice any change in engine operation characteristics. So it may be deactivated but dfm is also supposed to be almost undetectable in operation compared to afm.

I test drove a truck with the DFM active. It was literally seamless. If you bought it new on the MSRP it would indicate if it wasn't active-in the form of a small credit on the sticker.

 

[tyman]

There are still reports of DFM trucks on forums dropping lifters. So it’s still an issue unfortunately.

 

[CKN]

There are still reports of DFM trucks on forums dropping lifters. So it’s still an issue unfortunately.

Let's back up here. The lifters were faulty from the supplier. It's not a DFM issue per se.

" The service bulletin states that certain GM V8 engines may produce a service engine light, along with a misfire and peculiar engine noise, which is the result of faulty valve springs.

quote-""I have a friend who is tech at a big GM dealership and he told me about this last week. He state it is a supplier issue and they were told GM is working with the supplier and trying to figure out when the parts were made so they get them fixed asap on more vehicles. He said the lifters/springs are cracking from a manufacturing defect if there is no damage to engine he said they replace all of the springs/lifters on the side that is has the problem. Anything being built now should be fine.


https://gmauthority.com/blog/2021/0...sing-amount-of-v8-engine-valve-lifter-issues/

 

[4WD]

Our 2017 L83 just hit 60k - I put a Range plug in at 52k and started 5W30 at 60k … running great …
The new L84 is downright seamless … I have an extended warranty so might not fool with it …

 

[cpayne5]

Let's back up here. The lifters were faulty from the supplier. It's not a DFM issue per se.

I'm not sure that's completely accurate, unfortunately. There were a bad batch of lifters, and failure wasn't uncommon, but the forums and FB groups are still peppered with reports of lifter failure in vehicles manufactured outside of the timeframe of the supplied known bad lifters. There are a number of reports of people having lifter failures even after all lifters had been previously replaced, too.

Also, FWIW, there were two independent supplier issues. The first was valve springs, which affected early model year 2021 GM V8s. Corvettes, trucks, SUVs all affected. The supplier's specs were not in sync with GM's, so not all springs were faulty, but could have tested good from the supplier but fall outside of GM's specs and actually been potentially bad. The second issue was the lifters which affected mid-late 2021 MY vehicles build October 2020-March 2021 (if memory serves).

I've had a 2021 Tahoe (14k miles) and currently have a 2022 Yukon XL (8k miles). Both with the L87. Neither has had a lifter issue, fortunately. The Tahoe was an early-build 2021, but it never had the valve spring issue, either. The only time I think about lifter failure is right before long trips. Would rather not sit on the side of the road 8 hours from home with this issue (but any vehicle is capable of this!). Otherwise, I don't worry about it too much and just enjoy the ride.

 

[CKN]

I'm not sure that's completely accurate, unfortunately. There were a bad batch of lifters, and failure wasn't uncommon, but the forums and FB groups are still peppered with reports of lifter failure in vehicles manufactured outside of the timeframe of the supplied known bad lifters. There are a number of reports of people having lifter failures even after all lifters had been previously replaced, too.

Also, FWIW, there were two independent supplier issues. The first was valve springs, which affected early model year 2021 GM V8s. Corvettes, trucks, SUVs all affected. The supplier's specs were not in sync with GM's, so not all springs were faulty, but could have tested good from the supplier but fall outside of GM's specs and actually been potentially bad. The second issue was the lifters which affected mid-late 2021 MY vehicles build October 2020-March 2021 (if memory serves).

I've had a 2021 Tahoe (14k miles) and currently have a 2022 Yukon XL (8k miles). Both with the L87. Neither has had a lifter issue, fortunately. The Tahoe was an early-build 2021, but it never had the valve spring issue, either. The only time I think about lifter failure is right before long trips. Would rather not sit on the side of the road 8 hours from home with this issue (but any vehicle is capable of this!). Otherwise, I don't worry about it too much and just enjoy the ride.

Yes-my post mentions both the springs and/or lifters.

 

[cpayne5]

Yes-my post mentions both the springs and/or lifters.

You mentioned lifters, then quoted the valve spring issue, which is confusing. They're two distinct issues. As is the potential defective design causing lifter/pushrod failure.

The quoted comment from the webpage muddles the discussion even more by saying spring/lifters. Again - two distinct issues.

 

[clinebarger]

Had a 2019 DFM 5.3L Silverado come in just out of warranty.....Has had 3 bank 1 lifter sets & 4 bank 2 lifter sets replaced under warranty. #8 misfire with no movement of the intake rocker arm. Severely bent pushrod was found.

Recommended a used K2XX AFM 5.3L engine with a AFM delete using GM Bowtie Lifters/Non-AFM camshaft & a custom tune. Customer declined as it rivaled a new DFM engine install.

DFM will prove FAR more problematic than AFM if it hasn't already. K2XX chassis already had a sporadic history of bending pushrods on AFM cylinders.

 

[Cruisin'n5thgear]

Thanks for the info. Just bought a 22 Yukon XL as well. 10k so far.

 

[Falcon_LS]

I wish they would make DFM optional, it's proving to be a disaster. The rental '21 Suburban Z71 I had last year didn't have it, and while it got 18 MPG on average, you don't exactly get a fullsize SUV for fuel economy.

 

[tyman]

Let's back up here. The lifters were faulty from the supplier. It's not a DFM issue per se.

" The service bulletin states that certain GM V8 engines may produce a service engine light, along with a misfire and peculiar engine noise, which is the result of faulty valve springs.

quote-""I have a friend who is tech at a big GM dealership and he told me about this last week. He state it is a supplier issue and they were told GM is working with the supplier and trying to figure out when the parts were made so they get them fixed asap on more vehicles. He said the lifters/springs are cracking from a manufacturing defect if there is no damage to engine he said they replace all of the springs/lifters on the side that is has the problem. Anything being built now should be fine.


https://gmauthority.com/blog/2021/0...sing-amount-of-v8-engine-valve-lifter-issues/

Yes, so DFM equipped trucks are still have lifter issues. Nothing in my statement is wrong.

 

[tyman]

Had a 2019 DFM 5.3L Silverado come in just out of warranty.....Has had 3 bank 1 lifter sets & 4 bank 2 lifter sets replaced under warranty. #8 misfire with no movement of the intake rocker arm. Severely bent pushrod was found.

Recommended a used K2XX AFM 5.3L engine with a AFM delete using GM Bowtie Lifters/Non-AFM camshaft & a custom tune. Customer declined as it rivaled a new DFM engine install.

DFM will prove FAR more problematic than AFM if it hasn't already. K2XX chassis already had a sporadic history of bending pushrods on AFM cylinders.

Yup. Here's a guy with a 2021 AT4 that had issues with it brand new: https://www.silveradosierra.com/threads/lifter-failure-bent-lifter.741017/

 

[OVERKILL]

Had a 2019 DFM 5.3L Silverado come in just out of warranty.....Has had 3 bank 1 lifter sets & 4 bank 2 lifter sets replaced under warranty. #8 misfire with no movement of the intake rocker arm. Severely bent pushrod was found.

Recommended a used K2XX AFM 5.3L engine with a AFM delete using GM Bowtie Lifters/Non-AFM camshaft & a custom tune. Customer declined as it rivaled a new DFM engine install.

DFM will prove FAR more problematic than AFM if it hasn't already. K2XX chassis already had a sporadic history of bending pushrods on AFM cylinders.

This sounds a LOT more problematic than the HEMI lifter failure, sweet Jesus.

 

[tyman]

This sounds a LOT more problematic than the HEMI lifter failure, sweet Jesus.

Yup. The favorite ones are the guys who have lifters replaced and then 2-10k later, failing again.

https://www.silveradosierra.com/threads/lifter-failure.748379/

https://www.silveradosierra.com/threads/lifter-issues-again.748219/

 

[clinebarger]

This sounds a LOT more problematic than the HEMI lifter failure, sweet Jesus.

I would say so. I think I see the reasoning behind DFM as it no longer relies on the same 8 lifters to collapse over & over.....Which in theory should lessen Locking Pin wear when you spread it out over 16 lifters. But there's now 16 AFM lifters???

 

[OVERKILL]

I would say so. I think I see the reasoning behind DFM as it no longer relies on the same 8 lifters to collapse over & over.....Which in theory should lessen Locking Pin wear when you spread it out over 16 lifters. But there's now 16 AFM lifters???

Dear Lord, lol.

 

[doublebase]

I would say so. I think I see the reasoning behind DFM as it no longer relies on the same 8 lifters to collapse over & over.....Which in theory should lessen Locking Pin wear when you spread it out over 16 lifters. But there's now 16 AFM lifters???

I remember when this system was coming out, as I had a 2018 with the AFM, and the thought process behind it was seamless activation and more control through various engine ranges. I immediately thought, oh my lord they are going to really screw this up! And here at that time in 2018 they already were still having problems with collapsing lifters, faulty direct injectors and transmission torque converter failures. That’s the thing - the trannies just can’t handle the constant shifting that the cylinder deactivation requires on the GM’s. But GM just keeps on rolling with the latest/newest...there has never been a new technology idea that GM has not liked.