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Mass air flow sensor on a vehicle found on Long Island, NY.

What Is a Mass Airflow Sensor and How Can You Tell It Is Going Bad?

Posted at Fri, Nov 5, 2021 9:00 AM

The amount of electronically controlled components in modern cars is considerable and all of them are crucial in keeping your car running in top shape. Unfortunately, these electronic components can cease to function properly over time. This applies to the mass air fuel (MAF) sensor, which functions by ensuring the engine gets the right amount of fuel. While it might not stop working entirely, it could show some signs that it is on the way out, and to help you identify those signs our Westbury Toyota experts have written up a short, thorough guide.

What Is the Mass Air Fuel Sensor and What Does It Do?

The MAF ensures that the air going into the engine intake is always the correct amount. This is critical as it accounts for how much fuel is needed to maintain the proper ratio for air-fuel (AFR). The ideal AFR is supposed to be 14.7:1, which means that for every 1 pound (lb.) of fuel, there is 14.7 lbs. of air. However, in real world situations, the AFR will vary. When you are driving on cruise control, for example, the AFR could be 22:1, while acceleration could require an AFR of 12:1.

When the MAF sensor starts to malfunction, it will impact the engine control module (ECM), which ultimately results in an inability to correctly calculate fuel injection. When this happens, it will likely lead to issues with your vehicle.

Signs of a Failing Mass Airflow Sensor

There are several indicators that the MAF sensor may be failing, and some could be misconstrued as other vehicular issues. In order to be able to identify potential problems with the MAF sensor, it will be useful to become familiar with all the signs.

  • The exhaust smoke is black – if the AFR becomes too rich, it could lead to the exhaust smoke becoming black. When this happens, it could lead to problems with your vehicle’s catalytic converter.
  • The “check engine” light is on and stays on – A malfunctioning MAF sensor could lead to tripping the “check engine” light. However, there are numerous things that can lead to the “check engine” light coming and staying on, so using a diagnostic tool to interpret the diagnostic trouble codes may be useful in this circumstance.
  • Rough idling – A vehicle that has a properly functioning MAF sensor will idle smoothly. If the engine isn’t getting the right amount of fuel, it can lead to rough idling.
  • The engine hard starts – Starting the engine requires more fuel than when it is idling, but if the MAF sensor is malfunctioning it could lead to the ECM not directing enough fuel injection to get the engine started quickly.
  • Problems with acceleration – If your car or truck seems sluggish, particularly when it comes to accelerating to highway speeds or while passing another vehicle, it could be an indicator that the ECM is limiting fuel injection because of a faulty MAF sensor.
  • Decrease in fuel economy – A MAF sensor that is failing can lead to a negative impact on your fuel economy, as it can lead to the ECM erring on the side of rich AFR. When this happens, it means that more fuel is used than necessary, decreasing fuel economy.
  • Surging or hesitation – When you are in the process of maintaining highway speed or accelerating, you might notice that your car either hesitates or surges suddenly. Both are unsettling and are also signs that there may be something wrong with the MAF sensor.

The Next Steps

If after reading about the signs of a failing MAF sensor you think it is a problem you might have with your own Toyota, do not hesitate to contact us here at Westbury Toyota. We will book you in to have this crucial component inspected by one of our trusted mechanics in order to get you back out on the road in no time.

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