AFM or active fuel management is a GM/Chevy technology meant to improve gas mileage. AFM works by deactivating half of the engines cylinders under certain circumstances to reduce fuel usage. It essentially turns your V8 engine into a V4 which saves fuel.
GM claims fuel improvements ranging from 5%-15% depending on the engine. So why would you want to delete AFM? Unfortunately, it causes a number of issues for the Vortec engine family. The 5.3, 6.0, and 6.2 vortec engines that are equipped with AFM are known to have lifter failure, oil life monitoring system issues, and excessive oil consumption.
The excessive oil consumption caused by active fuel management combined with defective oil monitoring systems has caused numerous Vortec owners to experience premature catastrophic engine failure. Additionally, it frequently causes lifter failure which isn’t a cheap repair option either.
To prevent any engine problems caused by AFM you can either delete or disable the system.
What Engines Have AFM?
AFM is equipped on various Vortec engines. However, you need to look into your specific engine code as AFM is not used in every single engine.
- 5.3 Vortec: LY5, LC9, LH6, LMG, LS4
- 6.0 Vortec: L76, L77, LFA, LZ1
- 6.2 Vortec: L94, L99
- 3.9 Vortec: LZ8
- 4.3L EcoTec3 engines
- 5.3L EcoTec3 engines
- 6.2L EcoTec3 engines
- 3.6L V6 LGX
- 3.0L V6 LGW
- 4.2L V8 LTA
How Does AFM Work?
The top of the cylinder block has a valley cover over it which is called the lifter oil manifold assembly (LOMA). All Gen IV Vortec engine blocks have AFM towers and oil passages built into them. On non-AFM vehicles, the valley cover is completely flat and the towers and oil passages aren’t used. AFM vehicles come equipped with a special valley cover that has solenoids, oil pressure senders, and electrical connectors in it.
Additionally, the lifters on AFM engines are different. Cylinders 1, 4, 6, and 7 have taller lifters with oil holes in them. These are the cylinders that will shut off when AFM is activated.
When engine load is low AFM is activated. When this happens the GM ECU sends a signal to the valley cover which then opens the solenoids. Oil then flows to the lifters with the oil holes which causes the plunger inside of the lifter to close. When the plunger closes the lifters collapse and therefore do touch the pushrods which keeps both the intake and exhaust valves closed.
When load increases the valley cover solenoids close cutting oil off from the lifters. As the existing oil in the lifters funnels out they begin to function properly again re-engaging all 8 cylinders.
Understanding how active fuel management works is important for understanding how to delete it.
Benefits of Deleting AFM
The primary benefit of deleting or disabling active fuel management is in preventing engine problems. However, there are a few additional benefits. First of all, the V8 power is always available when you need or want it. And secondly, your Chevy will sound like a V8 and not like a little V4 Honda.
- Reduced likelihood of lifter failure
- Stops excessive oil consumption
- Louder exhaust notes
- V8 power is always there when it’s needed
How To Delete or Disable AFM
There are two options to fix the AFM issues on Vortec engines. Option one is to disable the AFM system, and the second option is to completely delete it. As we discussed above, the AFM system has a number of unique parts including the valley or LOMA cover and lifters. Additionally, it also has a different camshaft, a special oil pressure relief valve, and a high-volume oil pump.
Deleting the AFM system requires replacing all of these special parts with standard non-AFM parts. As you can imagine, this requires a good bit of labor and is also quite a bit more expensive.
Disabling AFM simply adjusts the engines ECU so that it never activates AFM. It essentially prevents the valley cover solenoids from ever opening which ensures your Vortec engine always stays in V8 mode.
How to Disable Chevy AFM
Disabling active fuel management requires either reprogramming or tricking the ECU into staying in V8 mode. To do so, you will need an AFM Disabler device. This device simply plugs directly into the OBDII port and starts working immediately. If you ever want to turn it back on or don’t want to take it to the dealer with AFM disabled, simply remove the device.
We recommend the Range Technology disabler since it is the only device on the market that doesn’t reprogram your ECU. Reprogramming the ECU voids engine warranty which is why this option is the best for anyone who still has some factory warranty left. The Range device comes in a few different colors, the different colors mean nothing. They do light up and are noticeable under the dash so they provide a few options for people who want different colors illuminating from their footwells. If you find the colors annoying you can simply put some tape over the LEDs.
Recommended Disabler: Range Technology AFM Disabler
Replacing the high-volume oil pump with a standard oil pump is still a good idea if you only disable the system. The excess oil the high volume pump delivers can cause oil buildup on the cylinder walls which then causes cylinder wall burning or scoring. While this will usually take quite some time to occur, it’s not a bad idea to prevent future internal engine issues.
How to Delete AFM
Deleting AFM is a bit more of a pain since it requires replacement of all of the AFM components. We generally only recommend deleting the system if you have failed lifters and have to do all of the labor anyways to replace them. Deleting the system also requires you using a disabler device or a custom tune so again, only do this if you really have to.
Here is a short checklist of what needs to be done to completely delete active fuel management:
- Replace your camshaft with a non-AFM camshaft
- Swap out the AFM lifters for standard lifters
- Replace the valley cover with a flat, non-AFM valley cover
- Disable the AMF system with the Range Technology Disabler, or custom tune it out
- Plug the pressure relief valve in the oil pan
- Swap the high-volume oil pump for a standard oil pump
A few random notes to go along with this as well. If you want to use a disabler instead of a programmer to turn AFM off then you need to leave the solenoid wires connected. If you do this, you can keep the AFM valley cover as well which will reduce some costs compared to replacing it.
When you keep the high-volume oil pump it flows excess oil. This excess oil will then seep into the bottom of the cylinder walls and burn. This can cause cylinder wall scoring/burning and lead to various performance issues and potential future internal repairs.
Should I Disable or Delete AFM?
Unless you have failed lifters we recommend disabling AFM. Deleting AFM requires replacing a lot of parts, gaskets, etc. which makes it more expensive parts wise, but also requires a lot of labor which is expensive you aren’t DIY’ing the project.
Additionally, disabling AFM allows you to turn it back on whenever you want. This lets you maintain your factory warranty and allows you to reinstall it if anything goes wrong from it being disabled.
If you do have failed lifters you can simply replace the lifters and then install a disabling device. The only reason we mention deleting it is that it doesn’t require a whole lot of extra labor to do so if you have to get to and replace the lifters in the first place.
In both circumstances we recommend replacing the oil pump, but I guess I’ll mention that not a lot of people actually replace this unless they are completely deleting the system. If you are just disabling it, it’s up to you but not a bad idea anyways.
GM & Chevy AFM Delete Summary
AFM lifters are known to fail more frequently than non-AFM lifters. Additionally, the system leads to excessive oil consumption. The excessive oil consumption can lead to oil levels running low, pressure dropping, and various major components such as the timing chain failing. Overall, the AFM system is responsible for a lot of very expensive repairs.
To prevent spending big money on AFM related repairs, the best option is to simply delete or disable the AFM system. Not only is it a good thing to do for preventative maintenance, it also gives you a better exhaust sound and keeps your car in V8 mode at all times.
Disabling the system is the best way to go unless you are already replacing lifters and just want to get rid of the whole system. Disabling it is the cheapest option and allows you to retain your factory warranty whereas a delete kit will be more expensive and void any warranty.
The only mentionable downside to disabling AFM is the decreased gas mileage it causes. AFM reduces gas usage anywhere from 5%-15% so removing the system will result in worse MPG’s. However, the money you save from not experiencing costly AFM related repairs more than outweighs the very small increase in gas costs.
Have you had any issues with your AFM system? Let us know in the comments and whether or not you went for a disable or delete kit.