The mass air flow (MAF) sensor measures the amount of air entering the engine. Based on input from the MAF sensor, a computer determines how much fuel should be injected into the engine. The sensor is usually located on or in close proximity to the air filter housing.
Problems with mass air flow sensors are common. A bad or contaminated sensor can cause a wide range of problems, including stalling (especially when the engine is cold), misfiring, and poor acceleration. A problem with the MAF sensor often causes the check engine or service engine soon light on the dashboard to illuminate.
To replace the MAF, the electrical connection and screws (or clamps) securing the sensor are removed, and the new sensor is installed.