• engine

What is a mass air flow sensor and what does it do?

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Updated 10 Oct 2019

Jason Unrau

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An engine needs three things to run: fuel, ignition (or spark), and air.

Sounds pretty simple, doesn’t it? Obviously, there’s much more that goes into it such as compression and timing, but by volume, the most important thing your engine needs to run is air.

Did you know that a normal 2.0-litre engine consumes around 1,000 litres of air per minute at idle?

It’s much higher while you’re driving! And it’s incredibly important that the air going into your engine is accurately measured so the right air-fuel mixture can be attained.

That’s where the mass air flow sensor comes into play.

What is a Mass Air Flow Sensor?

Every litre of air that passes through the engine must be accounted for.

Mounted in the air intake duct or air filter housing, a sensor detects the air density as it heads into the engine intake to be mixed with fuel.

Common mass air flow sensors use a heated platinum wire in the sensor that records an electrical resistance value in the car’s engine control module.

As more air is drawn into the engine, the airflow cools the heated wire, changing the resistance value.

The resistance difference is used to calculate how much air is being consumed.

What Does the Mass Air Flow Sensor Do?

With the air volume calculated, the computer adjusts the amount of fuel entering the engine.

Too much or too little fuel and the engine won’t run efficiently, or it can be damaged.

How Do I Know if There’s a MAF Sensor Problem?

If your car has a mass air flow sensor problem, it will definitely tell you about it – the Check Engine light will come on!

There are other symptoms that can occur such as:

  • Increased fuel consumption from the engine running rich (air-fuel mixture too high)
  • Rough idle
  • The engine can stall, especially when idling

How to Deal with Mass Air Flow Sensor Problems

If your Check Engine light is on due to mass air flow sensor issues, it first needs to be confirmed by a qualified mechanic.

Other faults can cause similar codes and symptoms, such as a faulty oxygen sensor or a vacuum leak.

Also, it’s possible that the MAF sensor is just dirty.

Special MAF sensor cleaner can remove any contaminants, potentially fixing the condition.

If the mass air flow sensor’s platinum element is broken or is otherwise truly faulty, it must be replaced.

What Does Mass Air Flow Sensor Replacement Cost?

For such a pesky problem, the repair is rather straightforward.

A new mass air flow sensor is installed, the trouble codes cleared, and the system monitored to ensure the results.

For most cars, you’ll pay around $220 to $360 for a replacement mass air flow sensor replacement, including parts and labour.

Luckily, AutoGuru is here to make it easy when searching for local mechanics to replace your Air Flow Sensor.

Grab a quick a quote and see how much you can save.

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Written By

Jason Unrau

Jason is a Canadian automotive content writer with a background in the auto service industry, but he’s been hooked on cars and mechanics since childhood.

One of his first cars was an ’80 Mazda RX-7 that’s sorely missed to this day. A ’68 Ford Torino GT, a ’66 Ford Country Squire Woodie station wagon, and a ’96 Suzuki GSX-R 750 have spent time in his fleet of cars, bikes, and trucks over the past two decades.

Jason’s pride and joy is under construction – a turbocharged ’88 Mazda RX-7 convertible. Also on his resume is CASCAR official certification.