Valve Timing Control System

To improve engine performance and reduce exhaust emissions, Vehicles are equipped with variable valve timing. This is accomplished through use of intake valve timing control solenoids located on intake camshaft pulleys. Intake valve opening and closing is controlled according to engine operating conditions as monitored by ECM. Input signals from mass airflow sensor, crankshaft position sensor, coolant temperature sensor, throttle position sensor and park/neutral (inhibitor) switch are used to determine intake timing.

Intake camshaft pulley position is regulated by oil pressure, which is controlled by valve timing control solenoids. Intake valve timing is controlled under the following conditions: engine is not idling, coolant temperature is 158-230°F (70-110°C), engine speed is less than 4600 RPM, engine load is high and transmission is not in Park or Neutral. During these conditions, solenoid is energized by ECM. This causes intake valve opening and closing time to advance and valve overlap to increase.