Some symptoms of a vehicle's mass air flow sensor going bad are difficulty starting the engine, engine stalling and hesitation during acceleration. These problems are similar to those caused by a faulty fuel pump.
When a car's mass air flow sensor goes bad, it prevents the engine from receiving the correct amount of fuel. This is because the sensor determines the volume and density of air entering the engine, and this information is used by the car's engine control until to adjust the flow of fuel. The correct mixture of air and fuel is necessary to maximize the engine's performance.
A bad mass air flow sensor produces an error code in the car's on-board computer and will cause the check engine light to illuminate. This problem is easily diagnosed by a mechanic with computer testing equipment or by the car's owner using a digital scanner available for rent at auto parts stores.
Some symptoms of a bad mass air flow sensor are due to the sensor being dirty but not defective. The sensor is located in the engine's air box, and can be removed with a screwdriver. The mass air flow sensor has two small exposed wires that may acquire particle build up. These can be cleaned using electrical contact cleaner or mass air flow sensor cleaner available at auto part stores. If vehicle's performance returns to normal after cleaning the wires, the sensor it won't need to be replaced.
In order to repair a moderately performing MAF sensor, the sensor must be removed and cleaned with alcohol or a special cleaning fluid. Then it must be completely air dried before reinstalling.