Air Induction System

Fig. 5 Digital electronic fuel injection engine controls:

The Air Induction system consists of the throttle body assembly, idle speed control and intake manifold.
Air enters the throttle body and is distributed to each cylinder through the intake manifold. The air flow rate is controlled by the throttle valves which are connected to the accelerator pedal linkage. Idle speed is determined by position of the throttle valves and is controlled by the Idle Speed Control (ISC) actuator.
Additional air for cold starts and warm-up is provided by opening the throttle valves further. This is accomplished by the ISC actuator moving out further in response to commands from the ECM.
The Throttle Body, Fig. 5, consists of a housing with two bores and two shaft mounted throttle valves connected to the vehicle accelerator pedal by mechanical linkage. Fittings are incorporated to accommodate vacuum connections. The end of the throttle shaft opposite from the accelerator lever controls the Throttle Position Sensor.
The intake manifold used with the DEFI system is constructed of aluminum and is of the dual plane design and incorporates an exhaust heat crossover passage since DEFI uses the EFE heat riser system.