Why Cylinder Deactivation Can Cause Engine Failure
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 Published On Feb 8, 2021

Here’s an in-depth look at how cylinder deactivation works and how it can potentially harm your car’s engine.


Cylinder deactivation is the process of turning off some cylinders on your car’s engine to save fuel and reduce emissions. It typically engages when the power of all cylinders are not required, such as when cruising or decelerating. In this video, we tear down a Honda J-series V6 engine with variable cylinder management (VCM) technology to see how the engine is able to turn off those cylinders and stop the intake and exhaust valves from moving using just oil pressure.


During VCM activation, oil pressure is sent from the head through a control solenoid that allows oil to flow through the rocker arm shafts. The oil pressure is received by the rocker arm, which activates a small piston to push against the spring loaded piston that holds the rocker arm assemblies together. This disengages the rocker arms that glide on the camshaft lobes with the ones that are connected to the valve springs – with return springs causing them to stay put. The result is the valves remain closed while the deactivated pistons are drawn up and down in the combustion chamber through the crankshaft which its connected to.



Typical problems with this system include oil being drawn into the vacuum in the combustion chamber caused by having the valves closed, fouling the spark plugs. Piston rings also wear (and may also align) causing oil to be consumed at a very rapid rate. The result is a lack of lubrication, worn rings and cylinder misfires. VCM turns off three of the cylinders which transmit vibrations through active engine mounts meant to dampen vibrations. These mounts eventually wear out causing vibration and noise to enter the cabin when the ECO light is on. Some Honda and Acura V6 owners have resorted to installing a resistor in the coolant temperature circuit (known as VCM Muzzler) to fool the computer into thinking it is not yet at full temperature and not engage VCM to avoid this issue.


The engine in this video was out of a 2005 Honda Accord Hybrid V6.

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Skip to section in the video:
0:00 Introduction
0:55 Teardown
3:21 How VCM Works
11:38 Problems Caused by Cylinder Deactivation
15:34 Final Thoughts


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