A Mass Air Flow Sensor works with the vehicle’s oxygen sensor to send signals to the Powertrain Control Module (PCM). While the oxygen sensor tells the PCM how much oxygen is leaving the engine, the Mass Air Flow (MAF) Sensor tells the PCM how much air overall is moving through the engine. With this information, the PCM can control the vehicle’s fuel injectors to change the fuel/air ratio going into the engine.
The most efficient ratio of air to fuel in an internal combustion engine is 14.7:1. Therefore knowing exactly how much air is flowing into the engine is critical for determining how much fuel needs to be injected. This is accomplished by keeping fuel pressure constant with a fuel pressure regulator and varying the amount of time the fuel injectors remain open, referred to as injector pulse width.
Some fuel management systems use other inputs to help the PCM fine tune this calculation, but the brunt of this number comes from the MAF sensor. A dirty MAF sensor will give you poor fuel economy and a slower throttle response. A failed MAF sensor can give you a wide variety of computer codes and engine problems depending on how it fails. Sometimes the engine will just be sluggish, buck, and chug. Other times it will not start at all, or will start and immediately die, or will run but not idle. Many times a computer code will be set and “check engine” light will come on, or not. This is how critical the MAF sensor really is to the proper operation of your engine. But there is no “one size fits all” symptom that gives away a failed MAF sensor.