Air Flow meter

Installed above the air filter box on the L-Jetronic system is a movable flap connected to a potentiometer which measures the amount of air being inducted into the system. The more air entering the system, the farther the flap is forced open.

At the same time the signal is being sent by the air flow meter, other signals are coming to the ECU from the throttle position switch and the air temperature sensor. All of these signals are integrated by the ECU to to determine how long the injectors should be held open. In addition to the flap of the air flow meter, there is a small bypass port which controls idle speed by increasing(or decreasing) the amount of air which passes through the air flow meter at idle. Because the measurement of the amount of air flowing into the engine is the primary determinant of the amount of fuel injected, it is critical that only air passing through the flow meter be allowed into the engine. Any leaks in the system will not be accounted for by the air flow meter, which can cause the engine to run lean (or not run at all).