Throttle Body: Description and Operation

Throttle Body Assembly:

The throttle body controls air flow to the engine as follows:
- The single butterfly-type throttle valve position is controlled by a conventional cable/lever throttle linkage.
- The plate position at idle is set by the lever contacting 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 throttle body housing is a single-piece casting made of aluminum.
- The throttle body has a single bore with an air bypass channel around the throttle plate. This bypass channel controls both cold and warm engine intake air as regulated by the Idle Air Control valve (IAC valve) which is mounted directly to the upper intake manifold.
- 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.

Other features of the throttle body include:
- a preset stop to locate the Wide Open Throttle (WOT) position.
- a throttle body-mounted Throttle Position sensor (TP sensor), which provides an electrical signal which is used as an input to the powertrain control module.
- a sealant that is applied to the top of the throttle plate and bore to reduce plate-to-bore leakage. The sealant should not be removed by cleaning.