Symptoms of a Bad or Failing Mass Airflow Sensor

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Mass Airflow Sensors (MAF) have the responsibility of reporting the amount of air entering the engine to the Powertrain Control Module (PCM). The PCM uses this input to calculate engine load.

There are several designs of MAF sensors, but the most common by far is the hot wire MAF sensor. The hot wire MAF has two sensing wires. One wire is heated and the other is not. The microprocessor (computer) inside the MAF determines the amount of air entering the engine by how much current is required to keep the hot wire about 200 ℉ hotter than the cold wire. Whenever the temperature difference between the two sensing wires changes, the MAF will either increase or decrease the current to the heated wire. This equates to more air into the engine or less air into the engine.

There are a number of driveability issues that arise from faulty MAF sensors.

1. Runs rich at idle or lean under load

These symptoms indicate a MAF that has a contaminated hot wire. The contamination can come in the form of spider webs, potting compound from the MAF sensor itself, dirt that gets attached to oil on the MAF from an over-oiled aftermarket air filter, and more. Anything that acts like insulation to the hot wire will cause this type of issue. The fix is as simple as cleaning the MAF sensor with an approved cleaner, which the technicians at YourMechanic can do for you if they determine that this is the root problem.

2. Constantly runs rich or lean

A MAF sensor that continuously over-reports or under-reports airflow into the engine will cause an engine to run rich or lean. If the engine control system is working correctly, you will probably never notice this except for a change in fuel economy. A trained technician will have to look at fuel trim status with the use of a scan tool to verify this. A MAF sensor that behaves like this will require replacement. Before replacing the sensor, however, the rest of the circuit should be checked for proper operation. If the circuit has an issue, replacing the sensor will not solve your problem.

2. Rough idle or stalls

A completely failed MAF sensor will not send any airflow information to the PCM. This prevents the PCM from accurately controlling fuel, which will result in an engine that either will idle roughly or not at all. Obviously, replacing the MAF sensor is needed in this case.


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Joel

19 years of experience
741 reviews
Joel
19 years of experience
Acura RL - Check Engine Light is on - Jacksonville, Florida
very knowledgeable and precise. able to fix electrical issues in my car. Right on time for the appointment.
Toyota Highlander - Check Engine Light is on - Jacksonville, Florida
Joel was very efficient with inspecting my vehicle. He told the issues with the vehicle and gave great advice on what needed to be done for the repairs. I will definitely use this service again.

Matthew

31 years of experience
639 reviews
Matthew
31 years of experience
Jeep Patriot - Check Engine Light is on - Norfolk, Virginia
Matthew was on time which was a relief, he is very knowledgeable and was easy to understand what was wrong and what was being done. I am recommending to friends and family due to the great experience Matthew gave me. Extremely professional 10/10
Mercedes-Benz E320 - Check Engine Light is on - Williamsburg, Virginia
MATT WAS AMAZING! HE EXPLAINTED EVERYTHING SO WELL! HIS EXPERTISE AS A MECHANIC IS EVIDENT AND I HIGHLY RECOMMEND HIM.

Michael

14 years of experience
501 reviews
Michael
14 years of experience
Ford Mustang - Check Engine Light is on - Decatur, Georgia
Michael was extremely courteous and knowledgable, he diagnosed and solved my issue in record time. Will definitely look to him next time I'm in need of a mechanic!
Chrysler Sebring - Check Engine Light is on - Atlanta, Georgia
Michael arrived on time and was efficient. He also explained the issues my car was having in an understandable way, and gave me good advice on what to do moving forward with the repairs.

Christopher

15 years of experience
41 reviews
Christopher
15 years of experience
Honda Accord - Check Engine Light is on - Fairburn, Georgia
Christopher was excellent! He explained everything in detail to make sure I understood. He was professional and provided me with the next course of actions to resolve my care issues. I'm glad he was sent to service my car.

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