waveforms > sensors > air flow meter > Air Flow Meter (Faulty Air Vane)

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Air Flow Meter (Faulty Air Vane) Waveform Notes

This particular Air Flow Meter (AFM) was used on early electronic injection systems and has the same operational qualities as the later 5 volt systems. The voltage should be seen to rise as the air vane is moved with no breaks or loss of continuity. The example shown clearly demonstrates that just as the vane moves a loss of contact is seen with the same fault occurring again as the throttle is released and the engine returns to idle.

A time base of approximately 2 seconds plus is used, this enables the operator to view the AFM's movement on one screen, from idle, through acceleration and back to idle again.

An AFM with this particular output would produce ‘flat-spots’ or ‘hesitations’ when driven. As the carbon tile has sustained damage the only way to rectify this problem is to change the unit for a new one. Removal of the plastic cover will invariably show the white plastic of the tile clearly visible through the carbon track, however this may only become apparent when the track is cleaned with a solvent spray such as carburettor cleaner.