Solenoid Valves
Some parts of the engine management system are operated by actuators. These actuators/solenoid valves are controlled by the ECU and regulate the negative air pressure from the vacuum pump or inlet manifold.

Idle Control Valves
Controlled by the ECU, the idle control valve is used to regulate the airflow to the engine while there is no throttle input from the driver, thus controlling the engines idling rpm.