Understanding AFM Lifters: What to Know About Active Fuel Management
Active Fuel Management (AFM) is GM’s clever tech aimed at boosting fuel efficiency. It kicks in when the engine’s cruising under light loads, like when rolling down the highway at a steady speed. Sounds great, right? But there’s a catch—AFM lifters can fail, and that’s a headache many GM owners face.
How Does AFM Work?
So, how does this AFM magic happen? It’s all about a special set of valve lifters that replace half of the usual ones in V6 and V8 engines. When the engine isn’t working hard, the ECU sends a signal to the Valve Lifter Oil Manifold (VLOM). This opens up solenoids, letting oil flow through the AFM lifters.
Here’s where it gets interesting: the oil pressure locks the pins inside the lifters, disconnecting the inner body from the outer one. This means the outer body moves, but the inner one stays put, keeping the valves closed. No air or fuel gets in, which means no power from those cylinders. But don’t worry, the pistons keep moving; it’s just the valves that are taking a break.
When it’s time to hit the gas or climb a hill, the ECU flips the switch back on, and all cylinders come back to life.
Why Do AFM Lifters Fail?
AFM lifters can be a pain, and their failure often boils down to a few key issues: oil problems, timing mishaps, and just good old wear and tear. Many drivers start noticing trouble around 70,000 to 80,000 miles, especially in models from 2014 to 2019. Those years have seen a lot of complaints, and some folks are even taking legal action.
What Happens When AFM Lifters Fail?
When AFM lifters go south, it’s not pretty. The affected cylinder loses compression, often because the latching pins fail, causing the lifters to become useless. This leads to misfires and can throw the whole engine out of whack.
Additionally, the VLOM can develop leaks, and low oil pressure might show up on OBD II readers. Most AFM issues are tied to oil quality and pressure. Dirty oil can clog things up, preventing the lifters from working right.
Signs of AFM Lifter Failure
Symptoms of AFM lifter failure are pretty much the same as engine misfires. Here’s what to watch for:
- Low power when accelerating
- Rough idling
- Stalling
- Unbalanced engine performance
- Fouled spark plugs
- Check Engine light coming on
Oil consumption might skyrocket, and that ticking noise from the valves could become annoying. If the AFM system is active, oil can end up in the combustion chamber, leading to sludge buildup.
How to Prevent AFM Lifter Failure
The best way to dodge AFM lifter issues? Avoid buying a car with an affected engine in the first place. If already in the game, keeping a close eye on oil levels and regular changes is crucial. The 6.2-liter L86 and 5.3-liter L83 engines in Chevy Silverados and GMC Sierras are notorious offenders.
Some folks suggest using aftermarket chips to disable AFM, which can help but may hurt fuel efficiency. Plus, there’s a risk of messing up the ECU if the chip isn’t set right.
AFM Lifters Have Failed: What Now?
If AFM lifters are failing, ignoring it isn’t an option. The engine’s future is at stake. The choices are basically to pay for a replacement or consider scrapping the car. In 2021, GM faced a lawsuit over this issue, with claims that they knew about the lifter failures and didn’t do enough to fix them.
GM has offered some solutions, like replacing lifter banks or even entire engines, with a five-year warranty. But many owners are still waiting for a permanent fix.
How Much Does It Cost to Replace AFM Lifters?
Replacing AFM lifters isn’t cheap. It’s often recommended to replace everything related, including lifters, guides, and the VLOM. While parts might not break the bank, labor costs can skyrocket, bringing the total to around $1,000 to $2,500.
