This week, we launched a new feature “Ask the Expert”. Congratulations to our winning question, asked by Philip Fourie, who wanted to know how to clean a MAF Sensor. We reached out to industry expert Mark Berkowitz to help answer.
What is a Mass Air Flow Sensor?
A Mass Air Flow sensor (MAF) is a critical component of an electronic fuel injection system in your car. It is installed between the air filter and the intake manifold of the engine. The mass air flow sensor measures the amount of air entering the engine or the air flow. The sensor passes this data on to the Engine Control Unit, ECU.
The air mass information is necessary for the ECU to correctly balance and deliver the correct amount of fuel to the engine. When a vehicle's mass airflow sensor is faulty or defective it can cause a variety of problems, and usually results in very poor performance from your engine.
Symptoms of a Faulty Mass Air Flow Sensor
A contaminated or failed mass air flow sensor cannot accurately measure the amount of air flow. This in turn causes the engine computer to miscalculate the amount of injected fuel.
As a result, a bad mass air flow sensor causes various driveability problems, including a no-start, stalling, lack of power and poor acceleration. In addition, a faulty mass air flow sensor might cause the Check Engine or Service Engine Soon light to come on.
It is not always immediately evident the MAF sensor is the culprit as the aforementioned problems are similar to low compression or low vacuum and will also show symptoms like when your vehicle has low fuel pressure from a faulty fuel pump.
However, be on the lookout for the following common symptoms:
• The engine is very hard to start
• The engine stalls shortly after starting
• The engine hesitates while under load or idle
• Hesitation and jerking during acceleration
• The engine hiccups
• Rich or lean idling
If you believe your car has a faulty mass air flow sensor, take it to a qualified mechanic so that a complete computer diagnostic can be run. In most cases, a faulty mass flow sensor has a specific code that will generate during computer diagnostics and is usually easy to determine with computer testing equipment.
Another method mechanics use is to measure the amount of air flow (mass air flow sensor readings) at different RPMs. They then compare the readings to the specifications or to the readings of a known-good mass airflow sensor.
Often mass air flow sensor readings are measured at idle, 1,000 RPM, 2,000 RPM and 3,000 RPM. A contaminated or bad air flow sensor will, in most cases, show lower air flow readings than a known good one. In some rare cases a bad sensor may show higher readings.
Of course, different engines will have different readings and the air flow depends on the engine design, the engine capacity and the ECU programming.
Can you measure you mass flow at home?
There are apps such as Torque which you can download on your phone. To connect the phone app to your car, you will need a Bluetooth adapter that plugs into the OBD connector of your vehicle.
The picture below shows the mass air flow readings taken by the Torque app.

Eliminating other causes


At times, a poor electrical connection at the air flow sensor connector could also cause the air flow readings to be out of range. For this reason, the air flow sensor connector terminals as well as the wiring needs to be carefully inspected.


Alternatively, if an air filter is not installed properly, or the air filter box is not properly closed, a piece of debris can get sucked into the mass air flow sensor and cause problems. Sometimes the debris can fall in during the air filter replacement. In this case, the repair is easy. The mass air flow sensor must be cleaned, and the air filter must be reinstalled correctly or replaced.



How to Clean a Dirty Mass Airflow Sensor

You should clean your mass airflow sensor every six months, or every time you service your car. Cleaning it when you change your air filter will be a good way to save both time and money.


• Remove the Sensor

To clean your mass airflow sensor, first, you must remove it. The sensor is in your car’s airbox housing, or air mass meter housing. When removing the sensor, be sure to never touch the wires, as they are delicate and small. If it is broken or damaged it will need replacement, prices start at R895.00 so it is best to be cautious.



• Clean the Sensor

Use a special mass airflow sensor cleaner, or oxygen sensor safe carb cleaner and spray it onto your sensor, follow the product instructions, making sure not to damage your sensor.


• Dry and Reinstall the Sensor

After cleaning your mass airflow sensor with either the cleaner, let it sit, for 20 minutes or more. The sensor must be completely dry before it can be reinstalled in your car, otherwise you may damage it.


Have a look at the following parts on Start My Car:


Mass Airflow Sensors:

Air Mass Sensors: