Air Flow Meter/Sensor: Description and Operation

Fig. 15 Air flow meter:

The fuel injection system or engine management system uses an air flow sensor to precisely measure incoming air. The sensor sends an electrical signal proportional to the measured air flow to the control unit, which uses this signal to determine the amount of fuel the engine needs.

The amount of air entering the engine is measured by the air flow sensor. As intake air is drawn past the air flow sensor flap, the spring-tensioned flap opens and in turn actuates a potentiometer inside the sensor. The varying resistance of the potentiometer provides a varying voltage signal (approximately 0-5 volts) to the control unit that is proportional to air flow. The air flow sensor also contains an intake air temperature sensor that measures the temperature of the incoming air.

Because proper fuel metering depends on accurately sensing or measuring the intake air, any umeasured air entering the system will cause a lean fuel mixture and poor running. To see how air leaks can affect engine running, remove the oil filler cap while the engine is running.