Every internal combustion engine or ICE uses fuel and air to create a mixture potent enough to easily combust. For an engine to perform as intended, the ratio of fuel and air that reaches the combustion chambers has to be perfect. This ideal ratio, also known as a stoichiometric mixture, ensures optimum performance.

If the ratio isn’t close to being ideal, the engine would either be running ‘rich’ or ‘lean’. In other words, it would either have too much fuel, or too much air in the mixture. Both these types of mixtures have major drawbacks in conventional applications. Multiple components come together to make certain that an engine is being fed with just the right amount of fuel and air, and the mass air flow sensor or MAF sensor is one of them.

Article updated on 12/17/21. Original publishing date 03/10/21

What is a Mass Air Flow Sensor? 

The mass air flow sensor, as its name suggests, senses the mass of incoming air. There are two main types of mass air flow sensors – the hot-wire and hot-film type. 

While they might sound quite different, they work quite similarly. Both sensors, in most cases, are located between the air filter box and the intake manifold of the engine.

Hot-wire Mass Air Flow Sensor

A hot-wire mass air flow sensor, unsurprisingly, makes use of a wire that’s heated for gathering data. This wire is positioned to come in contact with the incoming air stream and is also constantly on the receiving end of voltage that keeps it hot. The wire in this type of mass air flow sensor is made of a material that has a high temperature coefficient of resistance.

Thanks to this, even the smallest changes in temperatures of the wire will change its electrical resistance. The wire’s electrical resistance increases as its temperature rises, which in turn changes the current flowing through the circuit. 

This sensor makes use of Ohm’s law which states that for many conductors of electricity (the wire in this case), the electric current which flows through them is directly proportional to the voltage applied to them. 

When the incoming air stream flows past the wire, it cools it down and decreases its resistance, which in turn allows more current to flow through the circuit. The main objective of this type of mass air flow sensor is to measure the current flowing through the wire and convert it into a signal for the PCM. Thereafter, the PCM matches the mass of the air with fuel content for an ideal mixture.

Hot-film Mass Air Flow Sensor

A hot-film mass air flow sensor, on the other hand, has a more detailed reading of the air mass. This is because it doesn’t just measure air mass, but also the direction and pulsation of the air. A hot-film MAF can do this because it has two air mass sensing units next to each other. 

It operates just like a hot-wire, but because there are two sensors it’s able to communicate which one experiences a change in resistance first. As a result, it can convey information like the direction of the incoming air stream. 

This is beneficial because sudden opening and closing of the throttle valve can affect the air moving through the intake. The hot-film mass air flow sensor communicates the airflow signal which can then be accounted for.

Mass air flow sensors don’t rely on other sensors because they directly measure the mass of the air. As a result, it’s not affected by a shift in air density which can occur due to temperature or altitude changes. 

Nonetheless, mass air flow sensors can be integrated with temperature and humidity sensors to make readings even more detailed, while also acting as a secondary check to verify the operation of the MAF.

Symptoms of a Failing Mass Air Flow Sensor 

Since mass air flow sensors have an important role in the functioning of an internal combustion engine, even the smallest snag will exhibit symptoms. However, one has to keep in mind that none of these symptoms are exclusive to a failing mass air flow sensor.

Rough Idle

One of the most common symptoms of a failing mass air flow sensor is irregular or rough idling. An incorrect mix of fuel and air makes it difficult for an engine to fire how it should, especially when it’s idling. Here’s how you can tell if your engine is running lean. Lean condition is definitely a potential indicator of MAF troubles.

Turning Over Troubles 

With a failing mass air flow sensor, an engine would have trouble providing the right amount of fuel required for a start-up. While the engine is likely to still turn over, it will do so with a little more difficulty.

Lower Miles Per Gallon

As mentioned before, a mass air flow sensor keeps the air-fuel ratio in check and a sensor that’s on its way out could make an engine run rich. When this occurs, there’ll be a noticeable drop in fuel efficiency. In many cases, this is the only symptom for a while and one that can occur early on.

Acceleration Difficulties 

Hesitation, jerking, or even surging during acceleration can be a symptom of many things including an issue with the mass air flow sensor. This can occur when the car is being provided with more or less fuel than required.

Black Exhaust Smoke

While black smoke from an exhaust could also be a symptom of another problem, it doesn’t rule out the possibility of an engine running rich due to a faulty mass air flow sensor. The black smoke you see coming out the exhaust is usually just unburnt fuel. 

It’s important not to confuse blue smoke with black smoke. Blue smoke coming out the exhaust is an indicator of a whole different set of problems and often means that your engine is burning oil for one reason or another. 

Check Engine Light

When the PCM miscalculates the air-fuel ratio, it affects the performance of an engine. Consequently, one can expect either trouble codes related directly to the failing mass air flow sensor, or from components that aren’t operating correctly because of it.

Can You Fix a Failing Mass Air Flow Sensor? 

While a hot-wire mass air flow sensor is a widely-used component, it is still one of the most delicate and easily contaminated components on your vehicle. If you are faced with a failing mass air flow sensor, you could try and repair it. However, more often than not, the best thing to do is to place an order for a replacement.

When unplugging the mass air flow sensor, make sure to be as gentle as possible while avoiding touching the wires. The wires a MAF uses aren’t just small, but also quite fragile. While you could try cleaning it manually, your best bet would be to use a dedicated compressed mass air flow sensor cleaner. 

Physically touching the wire or film can damage it beyond repair. So instead of cleaning with a brush or something, it’s much better to use a dedicated MAF cleaner. Reinstall it once it dries and looks for the symptoms you were facing before. It also has to be said that cleaning is considered to be a temporary solution.

If it hasn’t completely solved the issue, it’s highly recommended that you order a fresh mass air flow sensor.

Intake Issues? 

Another thing to keep in mind is that you might have issues with your intake rather than your MAF. If there’s a hole in the intake somewhere between the MAF and the intake manifold, your engine will be getting unaccounted air. 

In other words, your MAF sensor will read one air density value, while the engine gets more thanks to that intake leak. Always check your entire intake before replacing the MAF. 

Get a New Mass Air Flow Sensor Now!

Almost every car manufacturer will replace your mass air flow sensor at a certain mileage as it is a wear item at the end of the day. While it can be more expensive than other minor maintenance procedures, a new unit will help ensure that your engine is running on the perfect mix of fuel and air.

Waste no time as Newparts.com has a wide range of OEM parts at the best prices. To find the mass air flow sensor that fits your particular car, simply head over to the Shop section on our website!