AFM

Reed_2021 · November 9, 2021

So for some reason my 2011 gmc sierra lately has been going into v4 at random times just for a few seconds then back to a v8. I took it the the GMC dealership and they told me nothing was wrong with the AFM but it still is doing it very randomly and when it goes back from 4v into v8 it takes a second and jerks a little bit. should I just get a AFM disabler or what im so lost on what is wrong.

Sharpz · November 9, 2021

Obviously its your truck, and your choice. I think the general consensus amongst early AFM trucks is to disable it, I think mainly to prevent the lifter tick issue. I honestly dont know why anyone would want this feature in a full size truck anyway.

dna9656 · November 9, 2021

From what I have read most folks disable the AFM before it destroys the engine. I think there is a way to turn it off with the right scanner.

swathdiver · November 9, 2021

18 hours ago, Reed_2021 said:

So for some reason my 2011 gmc sierra lately has been going into v4 at random times just for a few seconds then back to a v8. I took it the the GMC dealership and they told me nothing was wrong with the AFM but it still is doing it very randomly and when it goes back from 4v into v8 it takes a second and jerks a little bit. should I just get a AFM disabler or what im so lost on what is wrong.

That's normal operation. It's not really random, certain parameters are met allowing it to turn on and then off.

If you feel it, it's probably time for a new driver's side engine mount. Dirty old oil is AFMs worst enemy, keep it clean and fresh and the system is quite reliable.

Reed_2021 · November 9, 2021

just curious what would the divers side engine mount do?

Reed_2021 · November 9, 2021

also when driving it today it seem to get stuck in v4 and take a second to get back into v8 i do have a small cut in the exhuast could that effect it?

Grumpy Bear · November 9, 2021

2 hours ago, swathdiver said:

That's normal operation. It's not really random, certain parameters are met allowing it to turn on and then off.

If you feel it, it's probably time for a new driver's side engine mount. Dirty old oil is AFMs worst enemy, keep it clean and fresh and the system is quite reliable.

The above? That is rock solid advice.

Don't trouble trouble until trouble troubles you.

swathdiver · November 10, 2021

1 hour ago, Reed_2021 said:

just curious what would the divers side engine mount do?

Allow you to feel more engine vibrations such as when AFM kicks in and out. The mounts are fluid filled and last about 8 years or so.

1 hour ago, Reed_2021 said:

also when driving it today it seem to get stuck in v4 and take a second to get back into v8 i do have a small cut in the exhuast could that effect it?

Do you mean the motor was cruising along in V4 and then you stepped on it and it took more than a second to light off the other four cylinders? If yours were mine, I would put my Tech-2 on it and see what's going on with the AFM VLOM solenoids.

When these fail or slow down and get out of time, they take out the lifters which can lead to bigger problems. Anytime repairs are made in this area, it is SOP to replace the VLOM and all of the lifter trays.

Happen to be in Florida?

Reed_2021 · November 10, 2021

8 minutes ago, swathdiver said:

Allow you to feel more engine vibrations such as when AFM kicks in and out. The mounts are fluid filled and last about 8 years or so.

Do you mean the motor was cruising along in V4 and then you stepped on it and it took more than a second to light off the other four cylinders? If yours were mine, I would put my Tech-2 on it and see what's going on with the AFM VLOM solenoids.

When these fail or slow down and get out of time, they take out the lifters which can lead to bigger problems. Anytime repairs are made in this area, it is SOP to replace the VLOM and all of the lifter trays.

Happen to be in Florida?

Yeah it takes a little to set off the other 4 so I should check the code and see if anything pops up? I can look at the code at o Riley’s right?

Reed_2021 · November 10, 2021

Also no I’m not in Florida

dsr611 · November 10, 2021

2 hours ago, Reed_2021 said:

Yeah it takes a little to set off the other 4 so I should check the code and see if anything pops up? I can look at the code at o Riley’s right?

There's no code or CEL that comes on when this happens...you have to have a Tech2 scanner to read the status of everything "live"

Reed_2021 · November 10, 2021

I took it to the dealership to get checked but they said their is nothing wrong with my AFM but yet my truck still takes a second to go from v4 back into v8. could it be the VLOM filter or even the lifters themselves?

Grumpy Bear · November 10, 2021

52 minutes ago, Reed_2021 said:

I took it to the dealership to get checked but they said their is nothing wrong with my AFM but yet my truck still takes a second to go from v4 back into v8. could it be the VLOM filter or even the lifters themselves?

What it could be is you feeling the converter clutch unlock at the point of switching which it is suppose to do.

Reed_2021 · November 10, 2021

maybe but it just started doing it

Grumpy Bear · November 10, 2021

9 hours ago, Reed_2021 said:

maybe but it just started doing it

Here's a thought. Without a Tech-2 you have no idea 'when' the switch signal is being generated. Meaning the comment, "Over a second" to switch is without reference to anything but your expectations.

11 hours ago, Reed_2021 said:

I took it to the dealership to get checked but they said their is nothing wrong with my AFM but yet my truck still takes a second to go from v4 back into v8. could it be the VLOM filter or even the lifters themselves?

They did actually looked at it and didn't find anything wrong with the AFM.

I'd believe them.