Anything and everything you need to know about a Mass Air Flow Meter. If you need to know about other autoparts checkout the rest of our presentations.

1. What is a Mass Air Flow Sensor?
source: http://www.buyautoparts.com/howto/repair-mass-air-flow-sensor.htm

2. What is a
Mass Air
Flow
Sensor?
source:
http://www.buyautoparts.com/h
owto/what-is-a-manifold-
pressure-sensor.htm

3. What is a Mass Air Flow Sensor?
• A mass air flow sensor is used to find out the total of air entering a fuel-injected
internal combustion engine. The air mass information is necessary for the engine
control unit (ECU) to balance and deliver the correct fuel mass to the engine. Air
changes its density as it expands and contracts with temperature and pressure. In
automotive applications, air density varies with the ambient temperature, altitude
and use of forced induction and this is an ideal application for a mass sensor.
• There are two common types of mass airflow sensors in use on automotive
engines. These are the vane meter and the hot wire. Neither design employs
technology that measures air mass directly. However, with an additional sensor or
two, the engine's air mass flow rate can be accurately determined.
• Both approaches are used almost exclusively on electronic fuel injection (EFI)
engines. Both sensor designs output a 0.0–5.0 volt or a pulse-width modulation
(PWM) signal that is proportional to the air mass flow rate, and both sensors have
an intake air temperature (IAT) sensor incorporated into their housings.
• When a MAF is used in conjunction with an oxygen sensor, the engine's air/fuel
ratio can be controlled very accurately. The MAF sensor provides the open-loop
controller predicted air flow information (the measured air flow) to the ECU, and
the oxygen sensor provides closed-loop feedback in order to make minor
corrections to the predicted air mass. Also see MAP sensor.
source: http://www.buyautoparts.com/howto/what-is-a-manifold-pressure-sensor.htm

4. Mass Air Flow Sensor Description
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5. Mass Air Flow Sensor Description, pt 2
The mass air flow sensor works by reading the amount of
air passing the aperture in a given time. This is sent to the
vehicles computer via electrical pulses which can be
interpreted. This will allow the computer to adjust the fuel
added to the motor to create the correct internal
combustion. The mass air flow sensor not only reads the
amount of air flow but also the temperature of the air as
well. Air temperature is just as large of a factor as the
amount of air brought into the engine. The mass air sensor
will have a screen to protect the unit from debris. This is not
to stop dust or dirt but is intended to protect the engine
from any large debris that could enter the system.
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6. Mass Air Flow Sensor Breakdown
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7. Mass Air Flow Sensor Breakdown
The mass air flow sensor is a unit that sits at the front of the
air intake measuring the oxygen content of the air entering
the motor. The breakdown shown here is of the mass air
flow sensor housing and shows the individual parts that
make up the full unit. The unit is made up of an air temp
sensor, sample tube, metal foil sensing element, electronic
module and then the top cover and the flow tube. All of
these elements work together to properly sense the air
flow.
source: http://www.buyautoparts.com/howto/mass-air-flow-sensor-description.htm

8. Mass Air Flow Sensor Location
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9. Mass Air Flow Sensor Location, pt 2
The modern car has many electronic systems that control
the flow of air and fuel to the motor. The correct
combustion in the cylinders is key to the optimum
performance. The mass air flow sensor is the first sensor to
read the amount of air coming into the motor. The mass air
meter can be found just after the air box on all vehicles in
production today. The mass air meter may be located in a
different position down the intake plenum but will always
be before the throttle body.
source: http://www.buyautoparts.com/howto/mass-air-flow-location.htm

10. Mass Air Flow Diagnostics
The engine of a car is equipped with a mass air flow sensor that measures the volume and
density of the air entering the engine. In this way the vehicle's computer can calculate how
much fuel is needed to maintain the correct fuel mixture. Problems with mass air flow
sensors are common, but they rob the engine efficiency of your car, so if you notice that
your car doesn't run you should check the MAF. This could be a start to a fail.
By the time the check engine light illuminates on your dashboard, there is a symptom that
the mass air flow sensor has failed. To be sure that this is the problem the car's computer
must be checked.
source: http://www.buyautoparts.com/howto/mass-air-flow-diagnostics.htm

11. Mass Air Flow Diagnostics, pt 2
For MAF sensor problems you can analyze the computer yourself by attaching a
digital scanner on the vehicle's housing circuit and scan for any fault codes. You
can find scanners at auto shops and if some of them work differently they all have
the same function in the end. If there are trouble codes that may indicate a
deficiency in the MAF you can check them in the user instruction manual of the
scanner. If you found out the problems are with the mass air flow sensor, you
should take the car to an auto service center and replace it. The MAF being
repairable is very very rare.
When your engine runs lean failure of the MAF can be the cause, but there is not
a rule because it may indicate other problems than the MAF. The engine is having
trouble running and the car is idling erratically, tries to stall or the throttle actually
decreases at highway speed these can be symptoms of MAF failure.
source: http://www.buyautoparts.com/howto/mass-air-flow-diagnostics.htm

12. Mass Air Flow Diagnostics, pt 3
In some situations, mass airflow sensor begins to fail due to
contamination. In some cases there is the oil contamination and in
others there is dirt. In both cases, if the mass airflow sensor
becomes dirty the fix is to clean it or replace it.
The mass airflow sensor can be removed from the cars filter
housing. Spray the sensor's wires with electrical cleaner ONLY and
let the MAF air dry before you reinstall. Start the car and if the
engine's efficiency increases and the check engine light is off, the
problem was eliminated.
source: http://www.buyautoparts.com/howto/mass-air-flow-diagnostics.htm

13. Mass Air Flow Engine Snap Shot
The engine of a car is always being monitored by many systems but all the info is
fed to the main ECU. This info is available to the mechanic as an "engine snap
shot" which can tell the mechanic if there are sensors that are working correctly. If
there is an issue with the MAF (Mass Air Flow Sensor) the readings will be way out
of spec from what they are supposed to read. The mechanic can obtain the
correct specifications from the dealership.
source: http://www.buyautoparts.com/howto/mass-air-flow-diagnostics.htm

14. Air Intake
Cracks and
Leaks
source:
http://www.buyautoparts.com/ho
wto/air-intake-cracks-and-
leaks.htm

15. Air Intake Cracks and Leaks, pt 2
• The second most common issue that causes the mass air flow sensor to read
incorrectly is an air leak in the intake system. An air leak may not seem very
serious but it allow dirt and debris into the engine which can cause issues down
the road. When the air passes through the mass air flow sensor it is calculated at a
specific volume and if there is more or less air than the calculated amount it can
cause major issues for the motor. More air can cause a car to run lean which mean
that there is too much air and the fuel is burning too quickly, this means the
combustion will not have as much power to move the piston. Running lean can
also cause the detonation to take place in a specific location in the piston which
can cause damage.
• With a leak that is allowing air to escape from the intake the engine will run "fat"
which means there is too much fuel in the cylinders and not all of it is being
burned off during combustion. If all the fuel is not burned off it can be a big
problem. The unburned fuel can cause back firing and just a general lack of power.
Too much fuel means the engine will bog down and in some cased become
flooded which can cause the car to stall or loose significant power.
• In cases of mass air flow meter issues it is always a good idea to start by inspecting
the intake system. Many times the mass air is still reading right but the amount of
air that it has calculated has been changed to a leak in the system.
source: http://www.buyautoparts.com/howto/air-intake-cracks-and-leaks.htm

16. What is a Mass Air Flow Sensor?
The End
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source: http://www.buyautoparts.com/howto/repair-mass-air-flow-sensor.htm