Air-flow meter

1. Disconnect the accelerator cable from the throttle. - Release the pipes from the fastenings on the bracket under the throttle body. 2. Slacken the four fastening screws and remove the throttle body complete with potentiometer and constant idle speed actuator and separate them on the bench. - Remove the throttle body seal.

1. Connector
2. Measurement duct
3. Hot film sensor

AIR-FLOW METER

The air flow meter is of the "heated film" type. Its operating principle is based on a heated diaphragm interposed in a measurement duct through which the air admitted to the engine flows. The hot film diaphragm is kept at a constant temperature (~ 120°C above the temperature of the incoming air) by the heating resistance in contact with it. The mass of air crossing the measurement duct tends to withdraw heat from the diaphragm, therefore, in order to keep its temperature constant, a certain amount of current must flow through the resistance. This current is measured by a suitable Wheatstone bridge. Thus, the current is proportionate with the mass of flowing air.

This air-flow meter measures directly the mass of air and not the volume) thereby eliminating problems of temperature, altitude, pressure, etc. The correct operation of the air flow meter depends on the condition of the air cleaner, which must therefore be checked often.

REMOVAL/REFITTING

• Disconnect the battery (-) terminal. 1. Disconnect the electrical connection of the intake air temperature sensor. 2. Disconnect the electrical connection from the air-flow meter. 3. Slacken the two clamps fastening the corrugated sleeve to the air-flow meter.

1. Withdraw and remove the air-flow meter from the corrugated sleeve.