Air Flow Meter/Sensor: Description and Operation

Fig. 15 Air flow meter:

Intake air flow is measured by the air flow sensor. It is located in the intake passage between the air filter and intake manifold, and informs the ECU of the rate of air flow. A measuring flap swings in the airstream against the pressure of a spring, and is connected to a potentiometer.
The potentiometer transmits the measuring flap position to the ECU, which then uses this information to determine engine load. The air flow meter also controls fuel pump operation and idling. An adjustable idle air by-pass is used to regulate air/fuel mixture at low engine speeds.
Incorporated into the air flow sensor is the air temperature sensor. This sensor informs the ECU of the ambient temperature of the incoming air.