What is a mass airflow sensor and how does a maf work?

To keep your engine running you need air to combine with your fuel, at the set air fuel ratio. This mixture is what gives your engine the potential energy to combust. What amount of air and what amount of fuel though? Well you have a fuel injection map to scale up and down depending on what the engine needs. You have an air flow sensor to determine air density and the amount of air flow into the engine.

From this, your ECU can add the right amount of fuel to provide the perfect ratio. However, if your mass air flow sensor is faulty, your engine computer won’t know how much fuel to add.

This can lead the engine to run lean. Automakers know this and to avoid damage to the engine, when the sensor plays up, the ECU will make the engine run rich. This ensures that the car will still run. Albeit with a really rough idle and check engine light.

What is a mass air flow sensor?

Most people learn about it because of a check engine light. When it fails it will throw a trouble code to tell you it needs replacing. Your mass air flow sensor, or MAF, is found between your air filter and your intake plenum.

This means that when it is measuring air flow, it is after the filter and before the intake manifold. Telling the ecu exactly how much clean oxygen is being sucked or forced into the engine.

Imagine there’s a little wire finger that sticks into the air intake, in the path of the air. It gets heated and the air flowing past cools it. The signal that the MAF sends the ECU is directly responsible for how your car operates.

It was designed for fuel injection. With older, carburetted engines, the vacuum from the engine, past the fuel jets designated how much air and fuel was mixed and sent into the intake. When fuel injection came on to the scene, your engine needed to know exactly how much air to control exactly how much fuel was needed.

How does a MAF work?

Well you know that heated wire, that’s how.

Alright, we’ll elaborate.

The wire is heated. The amount of current that it takes to heat the wire tells the ECU how much air is flowing. So when the car is under very little load, like when it’s idling, it takes very little current to keep it heated.

When your throttle is wide open and lots of air is flowing past, it takes a lot of current to keep heated. This tells the engine that there is a lot of air flowing.

There is an electronic base map that tells the engine: x amount of current required = x amount of air flowing.

Based off of this, the ECU knows how much fuel to inject to result in the optimal air/fuel ratio.

Pretty neat hey.

How to tell if your mass airflow sensor is faulty

There’s a variety of symptoms of a bad mass air flow sensor.

Mainly you need to look for these things:

  • Check engine light. If the code is related to the MAF, then there you go.
  • Poor idle. If the car is stumbling or smells really rich, the engine computer is compensating for something.
  • IF your car develops a misfire or a big drop in acceleration. This can mean that the engine isn’t running optimally.

It’s also important to remember that your intake air temperature sensor is usually in the same fitting. All of these symptoms can also mean your IAT is faulty too.

What to do if my mass airflow sensor is broken?

Click here. We can easily have that fixed for you in no time at all. This is like shooting fish in a barrel for our partner garages, they can have you back on the road as cheap as possible, as quick as possible, as conveniently as possible.