Variable Valve Timing Solenoid: Description and Operation

PURPOSE
The Valve Timing Electronically Controlled (VTEC) Control Solenoid, mounted at the end of the cylinder head, supplies oil pressure to the VTEC hydraulic actuators mounted on the rocker shafts. When VTEC is disengaged, the primary intake valve opens and closes normally and the secondary intake valve opens only slightly (to prevent fuel "puddling" behind the valve) When VTEC engages, the valve train switches between single intake valve operation (with mild lift and duration) and two intake valves with high lift and duration. This system produces high fuel economy at low engine speeds and high output when desired.

OPERATION
Under the correct conditions the Programmed Fuel Injection Electronic Control Module (PGM-FI ECM) signals the VTEC solenoid valve to open by applying battery voltage. The open valve allows engine oil at operating pressure to enter the rocker arm assembly and move pins located in the primary, secondary and middle rocker arms, locking them together.