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The mass air flow sensor is an electronic air flow sensor, also referred to as an air flow mass meter, which measures air flow; the mass of air which is flowing through the car's engine, and is an important part of the Engine Control Unit (ECU).
The mass air flow sensor has an important part to play in the performance, power and efficiency of the car's engine. The mass air flow sensor is usually found in the plastic housing between the engine and the air filter. It is attached to the air hose at one end and the air filter box at the other. The 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, significantly reducing fuel efficiency, which in turn increases the car's CO2 emissions.
The mass air flow sensor works by measuring the air flow and sending these measurements to the car's ECU which, based on these measurements, will control the amount of fuel flowing into the engine at the point at which the ignition sparks.
The mass air flow sensor will, with continued use, wear out or stop working. When this happens, the performance of the engine is likely to be affected and engine emissions will be higher. A fault in the mass air flow sensor will cause the Check Engine light to show on the dashboard to indicate a problem with the mass air flow sensor. A broken mass air flow sensor can sometimes prevent a car from idling properly (the ability for a car's engine to run while it is not moving) and may cause the engine to splutter and stall. If there is a fault in the mass air flow sensor a replacement air flow mass sensor should be purchased.