ENGINE AND EMISSION CONTROL PARTS DESCRIPTION (Cont'd)

The air flow meter measures the intake air flow rate by taking a part of the entire flow. Measurements are made in such a manner that the E.C.U. receives electrical output signals varied by the amount of heat emitting from the hot wire placed in the stream of the intake air. When intake air flows into the intake manifold through a route around the hot wire, the heat generated from the hot wire is taken away by the air. The temperature of the hot wire is dependent on the quantity of air flowing over it, increased air flow causes the wire to be cooled to a greater extent. To compensate for the decrease in hot wire temperature, more current is supplied to the hot wire heating element to maintain the temperature at about the optimum level of degrees. The ECU detects the change in current and uses the information as an input signal corresponding to the rate of air flow.

The engine temperature sensor is located behind the distributor, it incorporates a thermister which converts changes in coolant temperature to a corresponding change in resistance. The resulting change in voltage is used as an input signal to the engine ECU.

The throttle sensor responds to the accelerator pedal movement. This sensor is a potentiometer which converts throttle valve position into a voltage signal which is input to the ECU. In addition, the E.C.U. calculates the opening and closing speed of the throttle valve. Idle position of the throttle valve is recognized by the E.C.U., and the ECU then maintains a steady idle. The throttle sensor is located on the throttle chamber air intake, adjacent to the throttle valve, its position is adjustable and must be set to optimum position in terms of throttle position to output voltage.