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Audi A4 MAF Sensor Replacement
 
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Pelican Technical Article:

Audi A4 MAF Sensor Replacement

Steve Vernon

Time:

1 hour1 hr

Tab:

$100

Talent:

*

Tools:

Flathead and Philips head screwdriver, 7mm socket

Applicable Models:

Audi A4 (2002-05)
Audi A4 Cabriolet (2003-06)

Parts Required:

New MAF

Hot Tip:

Do not use oiled air filters

Performance Gain:

Better mileage

Complementary Modification:

Replace air filter

The mass air flow sensor (MAF) is used to measure the amount and temperature of air that is entering the engine at any one time. The mass air flow sensor senses the total amount of air passing the sensor and allows the fuel injection system to adjust the fuel mixture to compensate for cold weather and/or high altitude conditions. The MAF also incorporates an internal intake air temperature sensor, which measures the temperature of the intake air.

The first indicator that you might have a problem with the MAF is the presence of a check engine light (CEL) on your dashboard. The check engine lamp can be caused by a wide variety of problems with the engine: you need to read the codes from the computer to get a starting clue as to what the problem is. However, the engine will not be operating at peak efficiency, and you will most likely experience a loss in power and a decrease in gas mileage as a result. It's best to get the problem taken care of relatively quickly, as running the engine in this condition can potentially cause damage to other components like the catalytic converters.

The computer will know if something is wrong with the MAF because it will compare the values being output by the sensor to "expected" values that it should be receiving. This common sense check by the computer helps diagnose problems with every component in the system. If the MAF becomes dirty and is falsely indicating to the engine that the car is receiving very little air while at full throttle, then the computer will most likely kick back an error code.

Vacuum leaks and other air leaks in the system can cause MAF sensor errors. If you have a crack or leak in your air intake downstream of the sensor, then the MAF will be sensing less air than the engine is actually receiving. You should carefully inspect all of your hoses, clamps and intake tubes for air leaks prior to replacing the sensor.

The new MAF comes complete in the air body housing so you will have to remove the complete housing to replace it.

The MAF is located in the front right corner of the engine compartment under the air intake duct (red arrow).
Figure 1

The MAF is located in the front right corner of the engine compartment under the air intake duct (red arrow).

Use a 7mm socket and remove the two bolts holding the plastic air intake duct to the front cross member (red arrows).
Figure 2

Use a 7mm socket and remove the two bolts holding the plastic air intake duct to the front cross member (red arrows). Note: someone had replaced a 7mm bolt with a Torx bolt on our project car; if your car was purchased used you should check the type and size of all hardware before attempting to remove.

Pull the plastic air duct back out of the grille and remove it from the vehicle (red arrow).
Figure 3

Pull the plastic air duct back out of the grille and remove it from the vehicle (red arrow). It will separate from the air box section of the duct in the middle.

The air box section of the duct connects into a clip on the EVAP valve.
Figure 4

The air box section of the duct connects into a clip on the EVAP valve. You do not need to disconnect this. You can just flip the duct out of the way (red arrow).

There are three components attached to the MAF: the wiring connection (red arrow), the air box (yellow arrow) and the intake tube (green arrow).
Figure 5

There are three components attached to the MAF: the wiring connection (red arrow), the air box (yellow arrow) and the intake tube (green arrow).

Disconnect the wiring connection by releasing the tab and then separating the connection (red arrow).
Figure 6

Disconnect the wiring connection by releasing the tab and then separating the connection (red arrow). Next, use a flathead screwdriver and loosen the hose clamp on the intake tube (yellow arrow).

Use a Philips head screwdriver and remove the two Philips heads screws holding the MAF to the air box (red arrow, one shown one hidden below the MAF).
Figure 7

Use a Philips head screwdriver and remove the two Philips heads screws holding the MAF to the air box (red arrow, one shown one hidden below the MAF). Remove the MAF from the vehicle.

The MAF is unidirectional but can only be installed one way.
Figure 8

The MAF is unidirectional but can only be installed one way. The sensor (red arrow, which you used to be able to clean) must face the incoming air. Installation is the reverse of removal.


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Comments and Suggestions:
David C Klasse Comments: does this apply to a B6 2008 A4 1.8 2.0? 4-cyl turbocharged engine?
November 6, 2016
  Followup from the Pelican Staff: No, only:
Audi A4 (2002-05)
Audi A4 Cabriolet (2003-06) - Nick at Pelican Parts
 

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