7 Bad MAF Sensor Symptoms (Replacement Cost)

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When a component is about to fail, it starts with exhibiting various signs. However, not every driver understands the signs of failing auto components.

When MAF sensors is bad or start failing, you’d notice that your car misfires intermittently, and the check engine light would come on, too.

But, those are not the only signs a failing Mass Air Flow sensor (MAF sensor) would show. This article explains the various bad MAF sensor symptoms you may experience when the sensor is about to fail. It is important that you replace the sensor once you start getting these signs.

What Is The Function of MAF Sensors?

The Mass Airflow Sensor (MAF sensor) is one of the crucial components that make up modern cars’ fuel injection systems. This sensor measures the amount of air a car takes from the outside – through the air filter – to regulate and maintain a specific air-fuel mixture inside the combustion chamber.

The MAF sensor sends signals to the car’s PCM/ECM, which processes the signals to decide the amount of fuel to be injected into the engine for proper performance.

So, if this sensor goes bad, the PCM won’t be able to decide the exact amount of fuel to be injected into the engine, and this can cause high fuel usage or low engine performance.

Notwithstanding, it is easy for the MAF sensor to get dirty or clogged; this mostly happens when the air filter is dirty. Once the sensor is dirty or clogged, it’d deliver incorrect readings to the car’s computer, which can cause/trigger any of the symptoms discussed below.

Bad MAF Sensor Symptoms

1. High Fuel Usage

Due to incorrect readings from the MAF sensor, the PCM/ECM may think your engine needs more fuel to mix with the air coming into the chambers; thus, more fuel would be injected into the engine, and this can cause a drastic decrease in fuel economy.

2. Engine Won’t Start

A bad Mass Airflow sensor can cause your car not to start. This happens when the PCM is unable to ascertain the amount of fuel needed to mix with the air coming into the engine chambers.

The improper air-fuel mixture can cause severe engine damage, and if the PCM senses that something like that is going to happen, it’d activate some precautionary systems and prevent your car from starting.

3.  Poor Acceleration and Engine Misfires

When the MAF sensor is about to fail, one of the things it’d cause is poor acceleration. This occurs because your car’s computer cannot maintain the specific air-fuel ratio needed for the engine to run smoothly.

Also, you’d most likely experience misfiring frequently as you drive. When these two scenarios happen concurrently, you’re most likely faced with a bad Mass Airflow sensor situation.

4. Rough Idling

A bad MAF sensor sending wrong signals to the ECM would cause the ECM to send more fuel or less fuel into the combustion chamber, and this can cause rough idling since the air-fuel ratio isn’t balanced.

5. Difficult to Turn Over, Hard Starting, and Engine Stalls

When you put your car key into the ignition and find it difficult to turn the key to start your car, that could be caused by a bad MAF sensor.

Also, while driving, if you constantly experience stalling – sluggish response from the engine – that could be caused due to incorrect air-fuel ration, and the culprit could be a bad MAF sensor.

6. Check Engine Light is On

While there are several reasons why the check engine icon or light would illuminate, a failing or bad MAF sensor can also cause that to happen.

When your car’s PCM/ECM detects a bad sensor, it’d trigger the check engine to light to come on. In this scenario, you need to troubleshoot the car – using an OBDII scanner – to find out the exact sensor that went bad.

7. Black Smoke Coming Out From The Exhaust Tailpipe

Since a MAF sensor is important to achieve a smooth combustion process, when the sensor is bad, which would cause incorrect air-fuel mixture in the combustion chamber, one of the resulting signs is black smoke coming out from the exhaust tailpipe.

This black smoke is caused due to “too rich” air and fuel inside the combustion chamber. If the smoke is not too dark/black, it means the air-fuel mixture is not too rich, but it’s definitely not in the right proportion specified for your engine.

MAF Sensor Replacement Cost

Bad MAF Sensor Symptoms

Replacing a bad MAF sensor would set you back $50 – $350. The sensor itself costs around $30 – $300 depending on the one you choose to buy. OEM MAF sensors are more expensive than “regular” aftermarket options. The labor cost is approximately $60; apparently, some mechanics charge higher than this average amount.

However, sometimes, all you need is to clean the sensor and everything would get back to normal. Cleaning the MAF sensor can be done by you, or at a mechanic workshop for about a $30 – $50 fee.

Frequently Asked Questions

What Makes an MAF Sensor Go Bad?

A dirty air filter would pass dirty air through the sensor into the engine. Over time, this can cause the sensor to become very dirty and begin to malfunction – output incorrect readings.

What are Mass Air Flow Sensor Problems?

The MAF sensor can get very dirty or physically damaged due to collision or excessive wear. These are the two commonest reasons why the sensor may start to fail and deliver incorrect readings to the PCM/ECM.

Where is the MAF Sensor Located?

As a key component in the injection system, an MAF sensor is installed between the air filter and the intake manifold. However, the exact position differs in different vehicles.


This article explains bad MAF sensor symptoms; when you start experiencing any of these symptoms, it is important to act promptly to fix the sensor before other components – or even the engine – get seriously affected.

Furthermore, it is important to note that you should replace the air filter in your car regularly, to ensure that the air coming through the vents is clean. A dirty air filter is one of the contributing factors to a malfunctioning MAF sensor.

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