The mass air flow sensor has the role of evaluating how much air is delivered to a fuel injected engine. This is important, as the air-fuel mixture needs to be constantly monitored and balanced by the engine control unit. Naturally, when the sensor is failing the symptoms tend to be related to this. Here are a few common ones.
1 - Bad Engine Performance
The engine loses power because the fuel isn’t properly burned. This is because the control unit that is used to balance the air-fuel mixture no longer has valid data to work with. If you experience noticeably reduced power and acceleration, a failing mass air flow sensor (MAF) can be one of the problems. A simple way to check if this is the case is to just unplug the MAF sensor and see if the engine runs better.
2 - Bad Gas Mileage
This is the symptom for a variety of problems with the engine or ignition. One of the problems that this symptom can point to is a sensor. Bad mileage occurs for the same reasons low engine performance does, badly optimized fuel burning.
3 - Engine Light is on
A simple, yet overlooked symptom is the engine light. This combined with the other mentioned symptoms can be very indicative of the nature of the problem you are facing. A failing mass air flow sensor will probably trip all 3 of the symptoms.