Throttle Body: Description and Operation

PURPOSE
The throttle body controls airflow to the engine.

CONSTRUCTION
The throttle body:

- is a single-piece die casting made of aluminum.

- has a single bore with an air bypass channel around the throttle plate. This bypass channel controls both cold and warm engine idle airflow control as regulated by an idle air control valve mounted directly to the throttle body.

OPERATION
The throttle body functions as follows:

- The accelerator cable, throttle lever and a cam rotate the throttle shaft from idle to Wide Open Throttle (WOT) position.

- The plate position at idle is set by the lever and a throttle return control screw. The throttle return control screw setting is permanent. Do NOT attempt to adjust idle/minimum plate setting with the throttle return control screw.

- The idle air control valve is an electro-mechanical device controlled by the Powertrain Control Module (PCM).

- The idle air control valve uses a linear actuator which positions a variable area metering valve.

FEATURES
Other features of the throttle body include:

- a non-adjustable, factory-set stop, to locate the idle position and a hard stop to locate the wide open throttle position.

- a throttle body-mounted throttle position sensor (TP sensor) which produces an electrical signal and is used as an input to the powertrain control module.

- a sealant applied to the downstream side of the throttle plate and bore to reduce plate-to-bore leakage.

NOTE: Cleaning may remove sealant. Do not clean.