The variable valve timing (VVT) actuator allows the timing of the camshaft(s) in your engine to be changed while the engine is running. Engine function requires that a small army of moving parts - from four to eight pistons, a crankshaft, camshafts, and as many as thirty two valves, along with dozens of other components - all march together at the same time. Like instruments in an orchestra, all of these components must be synchronized.
In an engine with traditional fixed timing, the relationship between moving pieces remains the same no matter what performance is called for. With variable valve timing, the engine timing can be adjusted on the fly to accommodate low, mid, and upper-range performance. In the process, it helps to improve efficiency, horsepower, and emissions. The VVT actuator allows the timing of the camshaft(s) to be advanced or retarded with changes in oil pressure to the actuator by way of the VVT solenoid.
Variable valve timing actuator replacement is a complex job since significant parts of the engine must be disassembled for access. In some cases, the timing chain and tensioners inside the front of the engine must be removed. Depending on the vehicle make and model, removal of the camshaft(s) might also be necessary, along with other valvetrain components.
Upon reassembly, care must be taken by the mechanic to ensure that all of the timing components are in proper alignment so that the engine will function as it should and to avoid any of the moving parts from coming into violent contact with one another upon startup. For this reason, the job is typically completed by an advanced level technician.