Does cylinder deactivation hurt the engine?

Engineers designed cylinder deactivation to be safe, and in modern vehicles it generally does not harm the engine when used as intended. It can improve fuel economy during light-load cruising by shutting off some cylinders.

In practice, cylinder deactivation—often called variable displacement or active fuel management—shuts off fuel and, in some designs, closes the intake and/or exhaust valves in selected cylinders while the rest of the engine continues to run. The engine control unit coordinates the switch to occur smoothly, typically under steady highway conditions and once the engine is warmed up, with reactivation happening automatically as load or speed increases.

What cylinder deactivation is and how it works

Cylinder deactivation is a technology used in many modern engines to reduce pumping losses and improve efficiency when full power is not needed. By temporarily removing the air-fuel charge from some cylinders (and in some designs physically deactivating those cylinders’ valves), the engine can operate with fewer active cylinders while maintaining overall drivability.

Key concepts behind the mechanism

The system relies on reliable hardware in the valve train, fuel system, and a robust engine control unit. When conditions are right, selected cylinders are temporarily shut down; when more power is required, the system rapidly reactivates them. The transition is designed to be imperceptible to most drivers and to protect engine components from abnormal stresses.

Benefits and advantages

There are several reasons manufacturers implement cylinder deactivation, primarily to boost efficiency and reduce emissions under light-load conditions.

• Improved fuel economy by reducing pumping losses and idle fuel use during steady cruising.


• Lower overall emissions in typical driving patterns when the engine runs on fewer cylinders at light load.


• Potential for smoother operation in some designs, as the system can help optimize torque delivery across a wider range of speeds.

In normal driving, most owners experience a practical balance between performance and efficiency, with the system switching invisibly in the background.

Potential downsides and considerations

Like any technology, cylinder deactivation has trade-offs and may present issues in certain situations or with older hardware.

• Perceptible transitions: some drivers notice brief, slight hesitation or a very mild roughness when cylinders are activated or deactivated, especially during cold starts or rapid changes in load.


• Wear and stress considerations: modern designs are engineered to minimize additional wear, but extremely aggressive or long-term cycling without proper maintenance could contribute to wear in valve-train components or actuators over very long intervals.


• Engine behavior if faults occur: a misfire in a deactivated cylinder or sensor fault can trigger warning lights or cause the engine to adjust power delivery, sometimes reducing performance temporarily.


• Not universal: cylinder deactivation is not present in every engine family. Some small-displacement or high-revving engines do not support it, and it requires ongoing software and hardware integrity to work correctly.

Overall, when the system functions as designed, it does not harm the engine and can be a net gain for efficiency. Problems tend to arise only when the system ages, is poorly maintained, or experiences a fault.

Maintenance, reliability and warranty considerations

Maintenance practices and manufacturer guidelines play a role in long-term reliability of cylinder deactivation systems. Following recommended service intervals helps ensure the switching mechanisms and related components stay healthy.

• Use the manufacturer-recommended oil and change intervals; hydraulic lifters and valve actuators rely on clean lubrication.


• Keep software/firmware up to date with official updates that optimize switching logic and error handling.


• Avoid attempts to disable or bypass the system; tampering can affect warranties and drivability.


• If you notice rough idle, loss of power, or an illuminated check-engine light, have diagnostics performed promptly to identify faults in the cylinder-deactivation system.

Proper maintenance and adherence to manufacturer specifications help ensure the technology remains reliable over the life of the vehicle.

Summary

Cylinder deactivation is a well-established tool in modern engines aimed at boosting fuel economy during light-load driving without compromising overall engine health. When designed, implemented, and maintained correctly, it does not harm the engine. Potential downsides are generally minor and related to transitions or faults, not inherent damage. For most drivers, the system works behind the scenes, delivering efficiency gains with negligible impact on everyday performance.

Bottom line for readers

If you own a vehicle with cylinder deactivation and it’s properly maintained, you should not expect the system to cause harm. Be attentive to any unusual idle, vibrations, or warning lights, and rely on official service channels to address issues promptly.

What is the downside to the start stop engine feature?

Start-stop technology's disadvantages include increased wear and tear on components like the starter, battery, and engine mounts, which can lead to premature failure and higher maintenance costs. Drivers may also find the system unsettling due to vibrations, noise, and the sensation of a delay when restarting the engine, especially in city driving conditions. Additionally, for some vehicles, immediate shutdown of a turbocharged engine without allowing it to idle can damage the turbocharger. 
This video explains some of the daily frustrations with start-stop systems, including engine restart delay and issues with air conditioning: 1mAuto WheelsYouTube · Jan 10, 2025
Mechanical and electrical disadvantages

• Component wear: Frequent starting and stopping places additional stress on the starter motor, battery, and alternator, requiring heavy-duty versions and potentially leading to premature failure. 
• Engine and transmission wear: The increased number of start cycles can lead to premature wear on internal engine components and potentially damage the engine mounts. 
• Turbocharger damage: In turbocharged engines, immediately shutting off the engine after running can prevent oil from circulating and cause damage to the turbocharger's components. 
• Exhaust system issues: The system can increase wear on parts of the exhaust system, such as the diesel particulate filter (DPF). 
• Battery drain: Running the air conditioning or other accessories off the battery when the engine is off can drain the battery more quickly. 

Driver experience and annoyance

• Noise and vibration: The initial implementation of these systems could be jarring, although newer systems are smoother. However, some drivers may still find the engine vibrations and noise unsettling. 
• Driving delays: Drivers may experience a slight delay when the engine restarts, which can be frustrating in situations requiring quick acceleration, like merging into traffic. 
• Annoyance: Many drivers find the constant cycling of the engine to be annoying and prefer to turn the system off whenever possible. 

Maintenance and cost

• Higher maintenance costs: The increased wear on components can lead to higher maintenance and replacement costs over the life of the vehicle. 
• Complex systems: The technology adds complexity to the vehicle's systems, which can make diagnosis and repair more difficult. 

You can watch this video to learn more about the potential downsides of start-stop technology, including the effect on engine wear: 44sScotty KilmerYouTube · Apr 20, 2018

Is AFM bad for my engine's longevity?

However, AFM lifters have a history of failing. Oil consumption has also been a problem. This is bad for performance. When upgrading the engine, we recommend you Disable or Delete the AFM System.

Does Honda VCM cause engine problems?

Yes, Honda's Variable Cylinder Management (VCM) can cause engine problems, including oil consumption, carbon buildup, and misfires, especially on older models. When cylinders are deactivated, oil can get past the piston rings and build up on cylinder walls, leading to fouled spark plugs and excessive oil burning. It can also cause a noticeable vibration or shudder during operation, which wears out engine and transmission mounts prematurely. 
Specific problems caused by VCM

• Oil consumption and fouling: The vacuum created by deactivated cylinders can suck oil past the piston rings. This oil fouls spark plugs and can contribute to misfires. 
• Carbon buildup: The oil that enters the combustion chamber can lead to carbon buildup on pistons and valves. 
• Misfires: Fouled spark plugs and carbon buildup can cause misfires in the deactivated cylinders. 
• Vibration and shudder: The transition between 6-cylinder and 3-cylinder operation can feel like a shudder or vibration, which can be felt throughout the car. 
• Premature wear on engine and transmission mounts: The vibration and shudder from VCM can cause premature wear and tear on engine and transmission mounts. 
• Catalytic converter issues: Excessive oil burned due to VCM can eventually contaminate and damage the catalytic converter, leading to a check engine light. 

How to address VCM problems

• Use a VCM disabler: Devices like a "VCM muzzler" can be installed to prevent VCM from engaging, which mitigates most of the associated issues. 
• Regular maintenance: Performing regular oil changes with high-quality oil and using a high-detergent fuel can help reduce some of the fouling and buildup. 
• Install an oil catch can: A catch can can help trap oil vapors from the intake, preventing them from being re-ingested into the combustion chamber. 

Is cylinder deactivation bad for the engine?

Yes, cylinder deactivation can cause engine problems, mainly related to increased wear on specific components like the hydraulic lifters and solenoids, which can lead to a "ticking" sound and eventual failure. Other issues can include unbalanced vibrations, injector imbalance, and potential issues with the turbocharger or exhaust system due to pressure pulses and temperature changes. Early models were more prone to problems, but modern designs are better, though the added complexity still introduces potential failure points. 
Potential problems with cylinder deactivation

• Increased wear on lifters and solenoids: The lifters in deactivated cylinders can wear out prematurely because they are being rapidly engaged and disengaged. The solenoids that control oil flow to the lifters can also fail over time. 
• Vibrations: When a cylinder is deactivated, a 4-cylinder engine running on 3 cylinders experiences unbalanced forces, leading to increased vibrations that can be felt in the cabin and potentially cause premature wear on engine mounts. 
• Oil consumption: A lack of lubrication due to worn-out piston rings in the deactivated cylinders can lead to increased oil consumption and a lack of lubrication. 
• Injector and exhaust system issues: Deactivating a cylinder can cause pressure pulses in the common rail, which is harmful to the injectors. It can also create issues with the turbocharger and exhaust manifold due to changes in exhaust gas pulses and temperature. 
• Software and mechanical failures: Errors in the software controlling the system can cause a misalignment of the intake valve rocker arm, leading to misfires or loss of power. The added complexity of the system can lead to premature failure of some components compared to a simpler engine. 
• Maintenance requirements: Vehicles with cylinder deactivation systems require the correct, full-synthetic oil to function properly. Using the wrong viscosity or type of oil can prevent the system from working correctly. 

Modern vs. older systems

• Older systems: Early cylinder deactivation engines suffered more significant problems with wear and tear over time.
• Modern systems: Newer engines have improved designs that have reduced many of these issues, but the added complexity still introduces potential points of failure. 

Conclusion
While modern cylinder deactivation systems are more reliable, they introduce additional complexity and potential failure points compared to non-deactivation engines. The main issues revolve around the increased wear on the valvetrain components, potential for vibrations, and the risk of failure in either the mechanical components or the control software.