I have read hundreds of AFM collapsed lifter threads but have not been able to find someone with my same issue where it has been solved. Looking for your expertise in the cause, not looking for advise to turn AFM off as that is the plan but I want to properly fix the issue first.
I have a 14 Silverado with a 5.3 with 50k miles and the issue I’m having is there is a pecking/knocking/rattle only when the truck is under light load while it is in V4 mode. Has anyone else experienced this where the noise occurs only while in V4 and while slightly accelerating?
The are no check engine lights, no noises at idle, no noise while running on 8 cylinders, no smoke, no oil usage, and it doesn’t appear to have lost any power.
The two possible problems I see are either:
1. One of the AFM lifters have failed in a way where it is not allowing the cylinder to deactivate which means the intake or exhaust valve will function like normal instead of closing during V4 mode. If this is the case is there any way to confirm this without a diagnostic scanner to put the truck in V4 at idle or to deactivate each cylinder? Is there any risk of further failure by not fixing this if I turn off AFM as it seems the “tabs” are just not disengaging within the lifter?
2. There is an issue somewhere within the VLOM portion with an actuator, oil port, something electronic that is preventing enough oil pressure to deactivate the lifter. If AFM is deactivated is there any risk with whatever is not working properly within this system?
Basically, I am fine with turning AFM off as where I drive there is likely minimal impact but I don’t want to turn it off just to cover up a problem that will resurface in the near future as I don’t intend on getting rid of the truck any time soon.
