Fluxing test

1. Disconnect the accelerator cable from the throttle.
2. Disconnect the two coolant inlet and outlet pipes from the throttle body.
3. Slacken the fastening screws and remove the throttle body complete with potentiometer and accelerator cable support bracket and if necessary, separate them on the bench.

• Remove the throttle body seal.

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.

NOTE: 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.

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

FLUXING TEST

• Proceed as described in the first four steps of the procedure for "Throttle body - Removal/Refitting".

1. Make sure that the throttle is in the closed position, then using tool no. 1.824.011.000 (C.2.0056) connected to the flow meter, check that the flow is within the specified limits.

AIR-FLOW METER

The air flow meter is of the "heated film" type.

REMOVAL/REFITTING

• Proceed as described in "Removal/Refitting Throttle body" up to disconnection of the corrugated sleeve.

1. Disconnect the electrical connection from the air-flow meter.