Throttle Body: Description and Operation

Throttle Body Exploded View.:

PURPOSE
The throttle body assembly is attached to the TBI and is used to control air flow into the engine, thereby controlling engine output. The throttle valve within the TBI 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. To prevent throttle valve icing during cool weather operation, engine coolant is directed through the coolant cavity in the intake manifold.

The throttle body also provides the location for mounting the throttle position sensor (TPS). Vacuum ports are located above or below the throttle valve to generate vacuum signals needed by various components (MAP, EGR and canister purge).


COMPONENTS

The TBI unit is made up of two major casting assemblies:

^ Fuel Meter Body

a. Fuel injector
b. Fuel Pressure Regulator

^ Throttle Body

a. Throttle Valve
b. Idle Air Control (IAC) Valve
c. Throttle Position Sensor (TPS)
d. Vacuum Manifold or Tubes:
NOTE: These are connected to the ports which supply the vacuum signals for the EGR valve, MAP sensor, and the canister purge system.