Is Honda cylinder deactivation bad?

Honda’s cylinder deactivation system, known as Variable Cylinder Management (VCM), is not inherently bad. It can improve fuel economy on light-load highway driving by temporarily shutting down some cylinders, but it adds complexity and, in older implementations, could cause roughness or hesitation. Modern versions are generally smoother, but the trade-offs—extra maintenance considerations and potential NVH (noise, vibration, and harshness)—remain relevant. This article explains how VCM works, its benefits and drawbacks, and how to evaluate it when buying or owning a Honda.

How Honda’s cylinder deactivation works

VCM is Honda’s approach to cylinder deactivation. Under light-load cruising, the engine management system selectively disables fuel delivery and spark to certain cylinders and coordinates valve operation so those cylinders are effectively taken out of the combustion process. When more power is requested, the affected cylinders are reactivated and the engine resumes full displacement. The overall goal is to reduce pumping losses and improve efficiency without sacrificing drivability.

When it engages and how reactivation feels

VCM typically engages during steady, light-load driving, such as highway cruising with low throttle input. As soon as the driver demands more power (accelerating, climbing hills, etc.), the engine software smoothly reactivates the deactivated cylinders. Most drivers notice a seamless transition, though some older or high-mileage systems can exhibit a brief, subtle change in idle sound or feel during the switch.

What drivers notice in practice

In many cases, the transition is imperceptible. In others, a brief vibration, tick, or momentary drop in smoothness may occur as cylinders switch on or off. The likelihood of noticeable changes depends on the model year, engine type, maintenance history, and driving conditions.

Benefits of VCM

The primary appeal of VCM is improved efficiency during light-load driving, which can translate into real-world fuel savings. The following points summarize the typical advantages observed in Honda’s VCM-equipped vehicles.

• Improved highway fuel economy during steady cruising due to reduced pumping losses.


• Lower CO2 emissions on trips that involve sustained light-load driving.


• Overall fuel savings that can be noticeable on long highway journeys, particularly for models with proven VCM tuning.

The magnitude of these benefits depends on the specific model, year, drivetrain, and how you drive. In city stop-and-go traffic, gains are usually smaller and less noticeable.

Drawbacks and reliability: what can go wrong

As a technology that adds complexity to the engine and its control systems, VCM comes with potential downsides. Here are common considerations noted by owners and service literature.

• Occasional rough idle or vibration as cylinders switch on or off, especially in older systems or after long periods between maintenance.


• Possible misfire or diagnostic trouble codes related to cylinder activation or fuel delivery, which may trigger software updates or service checks.


• Additional maintenance considerations and the potential for higher repair costs if a component in the VCM system fails.


• Carbon buildup or fuel-related issues in deactivated cylinders over long service intervals, though modern designs mitigate this with improved oiling and valve control.

Reliability varies by model year and maintenance history. Honda has issued software updates and refinements over time to address roughness and misfire concerns on certain generations, helping to improve smoothness in many later vehicles.

Is it right for you? How to evaluate

If you’re considering a Honda with VCM or assessing a used model, weigh your typical driving habits and the model year. Here are practical considerations to help you decide.

• If you do a lot of highway cruising at steady speeds, VCM can deliver meaningful fuel savings over the life of the vehicle.


• If most of your driving is urban with frequent stops, the benefits may be less noticeable and you might prioritize a smoother, more consistent power delivery.


• When shopping used, ask for the service history related to VCM, including any software updates or recalls, and take a test drive to judge how smooth the transitions feel.


• Confirm with the dealer or service advisor whether the specific model year has the latest VCM software and whether any known TSBs have been addressed for that vehicle.

Ultimately, the choice comes down to personal preference for fuel economy versus a preference for maximum smoothness and simplicity in the engine. Verification of the exact configuration and any updates for a given vehicle is advisable before purchase.

Summary

Honda’s Variable Cylinder Management can offer real fuel economy benefits under light-load highway conditions, but it adds complexity and can introduce occasional roughness in some years or models. Modern implementations tend to be smoother than earlier ones, and reliability has improved with software updates. For many drivers, the trade-off is favorable, especially on long road trips, while others who prioritize ultra-smooth, quiet operation in city driving may prefer a model without VCM or with newer refinements. Always verify the presence and current software status of VCM in a used Honda and test-drive to assess how the system feels in practice.

Should I avoid cylinder deactivation?

Is Cylinder Deactivation Bad? Engines can benefit greatly from cylinder deactivation. When paired with early or late intake valve closing technology, cylinder deactivation can help reduce fuel consumption by approximately five to 25% while maintaining high operating temperatures at low load conditions.

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. 

Does cylinder deactivation hurt the engine?

Yes, cylinder deactivation can hurt the engine, as potential long-term effects include increased wear on parts like pistons and rings, carbon buildup, and unbalanced vibrations. These issues can be mitigated by using high-quality synthetic oil and ensuring the system is properly maintained, but some manufacturers have had to recall vehicles to fix issues caused by faulty software controlling the deactivation transitions, notes this YouTube video. 
Potential harm to the engine

• Increased wear: The cylinders that remain active work harder, which can cause uneven wear on components like pistons, rings, and valves. Some studies suggest increased load on main bearings. 
• Carbon buildup: Inactive cylinders can experience carbon buildup, which may lead to future performance problems. 
• Vibration: The engine may vibrate or shutter more because it is operating on a different number of cylinders. 
• System failures: While rare, software glitches or component failures can occur. For example, a Mazda recall was issued for a software issue that could cause a valve to become misaligned, leading to engine problems, says this YouTube video. 

Mitigation and maintenance

• Use high-quality oil: Using a quality synthetic oil can help protect the engine, as the system is sensitive to oil quality, explains this YouTube video and a Reddit user. 
• Regular maintenance: Follow the manufacturer's recommended maintenance schedule to ensure the system operates correctly. 
• Don't ignore symptoms: If you notice unusual vibrations, misfires, or other issues, have the system inspected by a professional.

While some potential for harm exists, many car manufacturers have integrated cylinder deactivation technology successfully for years. The benefits of increased fuel economy are often seen as a positive trade-off, especially when the system is well-maintained and the correct oil is used.

Why do people not like cylinder deactivation?

And because you've dropped down from eight to four cylinders, you generally have to burn a little more fuel in each of those four cylinders in order to maintain the required amount of torque to keep the vehicle moving. So it's ultimately not as beneficial as it might seem on the surface.