Jump to content

AFM

Reed_2021
 Share

Recommended Posts

Reed_2021 Enthusiast

Reed_2021

Posted
Posted

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 Enthusiast

Sharpz

Posted
Posted

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 Enthusiast

dna9656

Posted
Posted

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 Senior Enthusiast

swathdiver

Posted
Posted
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.

  • Like 1
Reed_2021 Enthusiast

Reed_2021

Posted
  • Author
Posted

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 Senior Enthusiast

Grumpy Bear

Posted
Posted
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. 

  • Like 2
swathdiver Senior Enthusiast

swathdiver

Posted
Posted
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?

  • Like 1
Reed_2021 Enthusiast

Reed_2021

Posted
  • Author
Posted
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?

dsr611 Senior Enthusiast

dsr611

Posted
Posted
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"

  • Like 2
Reed_2021 Enthusiast

Reed_2021

Posted
  • Author
Posted

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 Senior Enthusiast

Grumpy Bear

Posted
Posted
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. 

  • Like 2
Grumpy Bear Senior Enthusiast

Grumpy Bear

Posted
Posted
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. 

  • Like 1

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing

  • Latest Articles

  • Posts

    • KARNUT
      OCI, not when but why?

      By KARNUT · Posted

      Well if you insist.
    • diyer2
      OCI, not when but why?

      By diyer2 · Posted

      You have to have the last word. 
    • Chuck FB
      summer road trips in the 2026 2500HD

      By Chuck FB · Posted

      I am sure that was quite the pass experience and not a great place to experience during the winter when the conditions are not good. I've seen video of that pass and also more detailed information and pictures about the wrecks at that one hair pin turn where tractor trailers have flown right off the cliff and I am sure from all the warning signs that you know the exact curve that was !. After all there is a reason why a song was made about Wolf Creek Pass !. By the way and I didn't realize this either when I bought my truck as its nothing I even thought of that would be programmed into the cruise control and this occurs in either the basic or the more advanced cruise that controls your distance behind a vehicle and that is the brakes going down a hill are being applied as soon as the vehicle goes a certain speed over the set cruise speed. While it certainly does force downshifts in the transmission as you found out with cruise on while going down hill, its also dragging the brakes as needed to keep the speed controlled to what the cruise was set to. For me, I find that unsettling simply because I have no concept then as to how MUCH brake input is being used a and just how hot are those brakes getting and the wear factor as well. I can see that system getting a person into trouble on long mountain grades while pulling a trailer as it would not only be standing on the brakes of the pickup without any driver input, it would also be automatically applying the trailer brakes and it could cause a run away unit by overheating the brakes. Its one thing on a shorter hill and if the driver allows it to do its thing but on a long mountain grade is where things could get so out of hand. As someone a while back on this forum said, they had someone following them at night I believe on a down grade and had the cruise set and the person behind them could see the brake lights being energized all the way down the hill. I figured when I saw your comment that you didn't know and would have no way of knowing that your truck was applying the brakes and that you would and rightfully so assume you only used the brakes when you pressed on the pedal to slow down more than the cruise set speed for the slower sharp curves. So its good knowledge to know this about the newer GM trucks, certainly when doing any descending on long mountain grades. In the future try kicking off the cruise and use the the manual mode on a pass to see what that is like as I know myself when I first experienced it I thought no way can this engine be holding me back this well and tried the same hill in manual mode and sure enough the engine was revving way up and still could not hold the trucks speed down like it could in cruise mode.    Fuel mileage, that is where a really low sleek type of car can do better at higher speeds, certainly it starts sucking fuel too but a tall pickup is pushing massive amounts of air and also allowing a lot more air under it and the tow mirrors as in elephant ears pushing through the wind  as well. Driving like grandpa is about as good as one can do when driving one of these if trying to get the best fuel economy they can. I bet these trucks would get the best mileage they can if driven on a freeway in Florida if not busy traffic at a sedate speed and that sea level elevation without hills, vastly different then Colorado !. 
    • KARNUT
      OCI, not when but why?

      By KARNUT · Posted

      It’s over for almost 24 hours. Are you playing Eddie Haskell? 
    • diyer2
      OCI, not when but why?

      By diyer2 · Posted

      Again, really you two.

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...