Throttle Body: Description and Operation

TBI Unit:

PURPOSE
Meters air/flow mixture entering engine.

LOCATION
On top of intake manifold.

OPERATION
When the throttle valve is opened via the accelerator cable and pedal, more air is introduced into the engine. The ECM monitors air density in the manifold and several other conditions and there for modifies the injector duration to maintain the correct air/fuel mixture.

Idle speed is controlled by air by-passing the throttle plate through the IAC valve air passage.

CONSTRUCTION
The Model 220 TBI unit consists of three assemblies:
- Fuel meter cover
Fuel pressure regulator
- Fuel meter body
Fuel injectors
- Throttle body
Two throttle valves to control air flow into the engine.
Idle air control (IAC) valve.
IAC air passage splitter for improved distribution of idle air flow.
Throttle position sensor
Vacuum ports locates at, above or below throttle valve to generate vacuum signals to various controls and accessories.