Air Flow Meter/Sensor: Description and Operation

Airflow Meter:

PURPOSE
The hot wire type airflow meter provides the ECU with a signal representing quantity of air entering the intake manifold.

OPERATION
The ECU uses its calculation of current required to maintain a constant temperature differential between wire elements as the measurement of air flow volume. Hot wire airflow meters are more accurate than mechanical types because they measure air density changes due to temperature fluctuations as well as volume flow.

CONSTRUCTION
The unit contains two wire elements, one at intake air temperature and the other electrically heated. The elements are located in a bypass adjacent to the main air flow passage through the meter. The bypass method of air flow measurement has several advantages, including:

1. Protects wire elements from shocks.
2. Reduces measurement error due to air flow pulsations.
3. Minimizes element contamination from dirt and backfiring.

Incorporated into the airflow meter is a potentiometer to provide idle fuel adjustment. It operates independently from the sensing elements. The factory set adjustment screw is sealed with a plastic plug and normally requires no attention.

LOCATION
Left side of engine compartment.