Skip the auto shop - Our mechanics make house calls

Symptoms of a Bad or Failing Mass Airflow Sensor

mass airflow sensor

Bad or Failing Mass Airflow Sensor Inspection

by a top-rated mechanic at your home or office

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.

HAVE SYMPTOMS OF CAR TROUBLE?
Get an $80 diagnostic
by a top-rated mechanic at your home or office.

Get a quote · Book an Appointment · Our expert mechanics come to you.

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.

HAVE SYMPTOMS OF CAR TROUBLE?
Get your car fixed at your home or office.

Get a quote · Book an Appointment · Our expert mechanics come to you.

3. 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.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Still not sure about your car's issue?
Diagnose your car
What kind of issue are you experiencing?
Brakes are squeaking
Car is not starting
Car is overheating
Car is shaking (vibrating)
Fluids are leaking
Heating and A/C
Smoke or steam is coming out of the car
Warning light is on
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
Veteran and Military Driver Laws and Benefits in New Mexico
The state of New Mexico offers a number of benefits and perks for those Americans who have either served in an Armed Forces branch...
P2159 OBD-II Trouble Code: Vehicle Speed Sensor B Range/Performance
Diagnostic Trouble Code (DTC): P2159 P2159 code definition Vehicle Speed Sensor B Range/Performance...


Related questions

Q: ABS light error codes

Hello. The ABS fuse will be located in the central junction box inside of the engine bay. It is likely that you have a short somewhere that is causing fuses to blow or interrupting another circuit. Your particular vehicle may...

Q: Rough idle with DTC P0171, engine stalls unless MAF sensor is unplugged - 2007 Volvo S40 2.4i

Your mass air sensor has most likely gone bad and/or is not giving correct data to the computer. Replace the sensor, clear the codes, and retest this.

Q: How do I reset the Best Average Fuel Economy?

The Best Average Fuel Economy setting is one of the driver information center (DIC) features. This setting allows you to view your most recent fuel efficiency over a selected distance, as well as the best fuel efficiency that you have...