Throttle Body: Description and Operation

Model B115 Throttle Body:

PURPOSE
The throttle body controls air flow into the engine based on driver input on the accelerator pedal and is also the source of vacuum signals used by other systems.

OPERATION
The Model B115 throttle body assembly is attached to the intake manifold air plenum, and is used to control air flow into the engine, thereby 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 almost closed, and air flow control is handled by the Idle Air Control (IAC) valve, described later. To ensure proper air flow by the throttle valve during cool weather operation, engine coolant is directed through the coolant cavity, on the bottom of the throttle body, to prevent throttle valve icing.

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.