Air Flow Meter/Sensor: Description and Operation

Fig. 88 Air By-Pass Screw:

The air flow meter measures the amount of are being drawn into the intake system. The meter has a flap that has a potentiometer connected to its pivoting shaft. As air flow increases, the flap is moved which in turn moves the potentiometer. The ECU provides a preset voltage signal to the potentiometer. When the flap moves the potentiometer, the ECU senses the change in resistance value as an air flow rate.
The meter is also provided with a bypass port. At idle, the amount of intake air is small and flows through the bypass port. The amount allowed to bypass the air flow meter flap is controlled by a screw. The bypass port is used to regulate the A/F mixture.