The Mass Airflow Sensor
The mass airflow sensor tells the car’s computer to add the proper amount of fuel based on the air coming through to the engine. A faulty one can increase emissions, cause the car to stall, and decrease gas mileage.
What causes it: Most mass airflow sensors fail because of a improperly installed (or never replaced) air filter. You should replace the air filter at least once a year to help prevent the airflow sensor from failing.
What you should do: Theoretically you can drive for a few weeks or even months with a broken MAF sensor. You will notice a decrease in gas mileage and over time the car will eventually start stalling a lot. At a shop, the replacement cost is between $200-$300 depending on the car, but that’s usually the cost of parts because the labor is relatively simple. It’s not terribly difficult to do on your own, but the process is quick enough you may want to let a mechanic handle the project in case the sensor doesn’t end up being the issue.