Throttle Body: Description and Operation

Typical Throttle Body Assembly:

The throttle body assembly is attached to the intake manifold air plenum, and is used to control air flow into the engine, controlling engine output. The throttle valve within the throttle body is opened by the driver through the accelerator controls. During engine idle, the throttle valve is closed, and air flow is handled by the Idle Air Control (IAC) Valve. To prevent the throttle valve icing during cool weather operation, engine coolant is directed through the coolant cavity on the bottom of the throttle body.

The throttle body also provides the location for mounting the Throttle Position Sensor (TPS) and for sensing changes in engine vacuum due to throttle valve position. Vacuum ports are located at, above, or below the throttle valve to generate vacuum signals needed by various components.