A mass air flow sensor, or MAF, monitors the amount and density of air entering the engine. I’m guessing you could figure that out from the name, but not many know that its an integral component in most modern engines.
It is usually installed inside the intake air duct, between the air filter and the engine.
The MAF sends its measurements to an engine control unit (ECU), which then uses that data to calculate when to deliver fuel, how much, and when to generate a spark. The MAF is sometimes used in conjunction with an O2 sensor that provides a “closed-loop” feedback in order to make corrections to that predicted air mass.
What Causes the MAF to Fail
Engines need a proper blend of air, fuel, and combustion to run efficiently. So a properly functioning MAF is crucial to a smooth ride.
Like anything mechanical or electrical, a MAF tends to wear down over the years. And while MAF problems aren’t specific to Volkswagen, it does feel that their tend to just wear down a lot faster.
Of course, any MAF will start failing if it gets too dirty to do its job. If an owner doesn’t regularly replace their air filter (or replaces it with a cheapo-version) it can cause a buildup of air impurities on the MAF.
What Happens When the Sensors Start Failing?
- The engine is hard to start
- The engine stalls or misfires
- Poor acceleration characterized by hesitation or “jerking.”
- Poor idle performance
- A negative effect on fuel economy
- A constant, headache-inducing, retina-burning warning light that will haunt your dreams (is it obvious I’ve had this problem before?)
Cleaning or Replacing the MAF
While you can clean a dirty MAF, in many instances its easier to just replace the unit.
A MAF at a dealership can cost anywhere between $75—$150 dollars, with labor costs adding another $150 to that total. You can try and clean the mass air flow sensor yourself by following the instructions in this article: