The air mass meter is located in the engine compartment usually adjacent to the air filter assembly. If you are going to clean the engine compartment of your car or truck, and it has a air mass meter, be sure to avoid getting water or degreaser on or around the air flow meter. The air mass meter or sometimes called the air flow meter is used to determine the airflow that is being delivered to your engine. The air mass meter does this by sending an electronic signal to the cars computer, and thus sends the correct signal to the fuel injectors that regulate the amount of fuel that is delivered to the engine. Be very careful not to touch or get any contaminates on the electrodes on the inside of the air mass meter, as this will cause the air flow meter to fail. If you are experiencing a hesitation on acceleration or a poor idle, this may be the result of a bad air mass meter. The best way to determine if you need a new air flow meter is to check the computer diagnostic codes. If you are experiencing a repeated failure of your air flow meter this may be due to the fact that you have an aftermarket performance air filter that uses an oil based filter element. This in some cases will damage the mass airflow sensors on newer cars and trucks.