Mass Air Flow Sensor – air mass meter fitted in the induction tract as part of the engine management system.

The sensor sits in the intake ducting immediately downstream of the air cleaner element and upstream of the throttle body, measuring the mass of air drawn into the engine and reporting it to the engine control module. That signal underpins the base fuelling and ignition calculations, so a contaminated or drifting sensor commonly shows as poor idle quality, hesitation, reduced power or raised fuel consumption before a fault code is stored.

The sensing element is fragile: handle the unit by its housing and do not attempt to clean the element with solvent.