The air metering unit works by measuring the air flow in the car's air intake system and sending these measurements to the car's ECU which, based on these measurements, will control the amount of fuel flowing into the engine and the point at which the ignition sparks. The air metering unit essentially controls fuel consumption ensuring the engine is running as efficiently as possible.
An engine needs the correct amount of air and fuel flowing through it in order for the fuel to burn in the cylinders and for the engine to ignite or spark at the right time. If the ignition sparks at the wrong time, there will be less power in the engine and it will try to make up for this by using more fuel, which significantly reduces fuel efficiency, which in turn increases your car's CO2 emissions.
The air metering unit has an air flow sensor, also called an air flow meter, which works by measuring the air flow and sending these measurements to the ECU. The ECU will then, based on these measurements, control the amount of fuel flowing into the engine and the point at which the ignition sparks.
The air metering unit will, over time, wear out or stop working. When this happens, the performance of the engine could be affected and consumption of fuel and engine emissions will be higher. A fault in the air metering unit means the engine will not be working properly or efficiently. A faulty air metering unit will cause the Check Engine light to show on the dashboard to indicate a malfunction with the air metering unit. A broken air metering unit can sometimes prevent a car from idling properly (the ability for a car's engine to run whilst it is not moving) and may cause the engine to splutter and stall. If there is a fault with the air metering unit, a replacement air metering unit should be purchased.