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Pelican Technical Article:

MAF Sensor Replacement

Steve Vernon

Time:

1 hour1 hr

Tab:

$150

Talent:

**

Tools:

Flathead screwdriver

Applicable Models:

Mercedes-Benz C350 (2008-15)
Mercedes-Benz GLK350 (2010-15)

Parts Required:

New MAF

Hot Tip:

Do not use oiled filters

Performance Gain:

Better mileage

Complementary Modification:

Replace air filters

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 that 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.

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.

You will need to remove the engine covers and air intake ducts to perform this work. Please see our article on engine cover removal.

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 under the engine covers at the rear of the engine (red arrow).
Figure 1

The MAF is located under the engine covers at the rear of the engine (red arrow). You will need to remove the covers first so please see our article on engine cover removal for additional assistance.

With the air filter covers off you can see the MAF sensor housing at the rear of the engine (red arrow).
Figure 2

With the air filter covers off you can see the MAF sensor housing at the rear of the engine (red arrow). There is a vacuum line that runs over the MAF that is quick and easy to remove (yellow arrows).

Disconnect the end on the left side of the engine compartment by squeezing in the plastic where it is ridged and then wiggling the connector off (red arrows).
Figure 3

Disconnect the end on the left side of the engine compartment by squeezing in the plastic where it is ridged and then wiggling the connector off (red arrows). Sometimes it helps to gently push the hose on a little further before squeezing the connector.

The other end is connected to the throttle body.
Figure 4

The other end is connected to the throttle body. Push down on the two tabs (red arrows) and gently wiggle the connection off.

The MAF sensor comes with a plastic mounting piece that has two plastic clips that mount to the rear of the intake manifold.
Figure 5

The MAF sensor comes with a plastic mounting piece that has two plastic clips that mount to the rear of the intake manifold. Using your hands gently pry these clips off the mount in the direction of the red arrows and slide the MAF and mount upward.

Use a flathead screwdriver and unclip the metal clip on the rear of the housing (red arrow).
Figure 6

Use a flathead screwdriver and unclip the metal clip on the rear of the housing (red arrow).

You can now lift the MAF housing up.
Figure 7

You can now lift the MAF housing up. This photo illustrates the actual sensor part of the MAF behind the protective screen (red arrow). The connection to the MAF is small and can be easily damaged so turn the MAF housing on its side to give you better access to the connection (yellow arrow).

Use a small flathead screwdriver and gently release the clip (red arrow) and separate the connection.
Figure 8

Use a small flathead screwdriver and gently release the clip (red arrow) and separate the connection.

With the MAF out of the car you can try spraying the film sensor section of the MAF (red arrow) with cleaner but I have never had any success with this method.
Figure 9

With the MAF out of the car you can try spraying the film sensor section of the MAF (red arrow) with cleaner but I have never had any success with this method. I always end up replacing the sensor.

Clean the connecting gasket area around the elbow pipe and check for any cracks in the pipe before installing the new MAF (red arrow).
Figure 10

Clean the connecting gasket area around the elbow pipe and check for any cracks in the pipe before installing the new MAF (red arrow). Installation is the reverse of removal.

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