Variable Valve Timing System Parts

What are the variable valve timing components and where are they located? 

Variable valve timing allows the valves that bring air into the cylinders during the intake stroke and exhaust gasses out during the exhaust stroke to open slightly early or later, and sometime for a longer or shorter amount of time.  This allows the engine to consume less fuel at low revolutions per minute, intake more air, and have a better combustion at high RPMs.  

Almost every car manufacturer has developed its own unique system to vary the valve timing.  Many of these rely on a process called camshaft phasing.  In camshaft phasing, an electronically controlled solenoid allows oil to flow to a camshaft actuator or phaser attached to the camshaft sprocket.  The oil shifts the phaser, which turns the camshaft relative to the sprocket.   That means the camshafts position relative to the crankshaft is changed, which changes when, in the pistons rotation, the valves open and close.  Some engines phase only the intake valves, while other have phasers for both the intake and exhaust valves.  Each cylinder bank, of course, has its own phaser or phasers. 

Another well-known system is Honda’s famous “Variable Valve Timing and Lift Electronic Control,” better known as VTEC.  The VTEC system has some cam lobes that are larger than the ones normally used.  These ride on rocker arms that aren’t directly connected to any valves.  There’s an electronically controlled solenoid that pushes in a pin that connects the free rocker arm.  Then the larger cam lobes essentially take over and change the valve timing.  That’s how the VTEC kicks in, yo. 

How do I know if my ­­­­ variable valve timing components need to be replaced?   

Problems with the variable valve timing can reduce the performance of the engine.  The camshaft may become stuck in a particular timing, which means you don’t get the benefits of variable valve timing at either low or high engine speeds.  The engine might stutter and stall out at low speed due to a too lean fuel-to-air ratio.  Conversely, top end performance might suffer.  You might also hear clicking noises from the valve train.  Often, if you are having variable valve timing problems, your check engine light will come on. 

Oil problems can take their toll on the hydraulics that run the variable valve timing system.  Thick, dirty, or sludgy oil can clog up the phaser or the solenoid.  That’s the major way for these parts to become stuck.  Thin oil could also cause premature wear inside the moving parts.  The solenoid can also suffer electronic failure if any of its wiring burns out. 

Can I replace the variable valve timing components myself?  

The variable valve timing solenoid is fairly easy to replace.  Replacing the variable valve timing actuator, on the other hand, is highly technical and should be left to a professional mechanic.  Replacing the actuator involves removing the timing cover, opening up the valve cover, removing the timing belt or chain, and setting the camshaft in a specified position, before you can remove the actuator. 

Replacing a variable valve timing solenoid is much easier, and can be handled by an experienced do it yourselfer.  You can access the solenoids by removing the timing cover.  Then you can disconnect the solenoid wiring harnesses, and remove the bolts that hold in the solenoids.  Then you can simply pull the solenoids straight out.  Reverse these steps to put in the new solenoids.