Sneakers
Just sneakin' around....
I've had my GMC Sierra 1500 since 2014. It came with a feature (AFM) that turns off 4 cylinders to run in an economy mode when 8 cylinders just aren't needed. I didn't see it doing a whole lot as far as fuel savings, but knew it was there. At lower speeds it would kick into "V4" mode and drop into high gear (6th), and you could feel a distinctive rumble from the drive train. Annoying, but not a big problem.
In the past few days I came across a series of YouTubes on AFM. It's a huge problem. AFM "turns off" 4 cylinders by manipulation the hydraulic lifters associated with cylinders 1, 4, 6 and 7 on the 5.3, 6.0 and 6.2 liter motors. These lifters have a very high failure rate. When they fail, it can cause catastrophic damage to the cam shaft, and in extreme cases, cause the pistons to strike the valves. Extremely expensive repairs. Class action suits have been brought against GM. There are kits available to retrofit the engine to remove the AFM (also called DoD Displacement on Demand). There are also OBDII plugs that turn off AFM, or you can flash the computer to turn it off permanently. Reprogramming to turn off AFM seems to help, but there have still been cases of lifter failure.
Seems the base cause of the failures is related to oil flow. Regular oil changes help mitigate the problem. There are also some internal cover bolts that come loose, not properly secured at the factory, that reduce oil flow to the lifters, and a small oil screen in the lifter oil delivery system that can clog. Unfortunately, you can't examine any of these without removing the intake manifold. Not a job for the novice.
One other thing you can do to suppress AFM is manually select the gear range so it doesn't drop into high gear. If you have an automatic with manual shift override, select "L" or "M" on the shifter and manually increment to 5th gear. It will shift normally in gears 1-5 but not drop into 6th, and the AFM won't engage. But you have to do this every time you restart the vehicle.
Anyway, it has me a bit concerned, but not much I can do about it right now. Just thought I'd pass this on as it's a very popular motor series. LOTS of videos on the failures and delete kits.
In the past few days I came across a series of YouTubes on AFM. It's a huge problem. AFM "turns off" 4 cylinders by manipulation the hydraulic lifters associated with cylinders 1, 4, 6 and 7 on the 5.3, 6.0 and 6.2 liter motors. These lifters have a very high failure rate. When they fail, it can cause catastrophic damage to the cam shaft, and in extreme cases, cause the pistons to strike the valves. Extremely expensive repairs. Class action suits have been brought against GM. There are kits available to retrofit the engine to remove the AFM (also called DoD Displacement on Demand). There are also OBDII plugs that turn off AFM, or you can flash the computer to turn it off permanently. Reprogramming to turn off AFM seems to help, but there have still been cases of lifter failure.
Seems the base cause of the failures is related to oil flow. Regular oil changes help mitigate the problem. There are also some internal cover bolts that come loose, not properly secured at the factory, that reduce oil flow to the lifters, and a small oil screen in the lifter oil delivery system that can clog. Unfortunately, you can't examine any of these without removing the intake manifold. Not a job for the novice.
One other thing you can do to suppress AFM is manually select the gear range so it doesn't drop into high gear. If you have an automatic with manual shift override, select "L" or "M" on the shifter and manually increment to 5th gear. It will shift normally in gears 1-5 but not drop into 6th, and the AFM won't engage. But you have to do this every time you restart the vehicle.
Anyway, it has me a bit concerned, but not much I can do about it right now. Just thought I'd pass this on as it's a very popular motor series. LOTS of videos on the failures and delete kits.
Seems Ford went with something similar the year after mine.
