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Pelican Technical Article:

MAF Sensor Replacement

Steve Vernon

Time:

30 minutes30 mins

Tab:

$100

Talent:

*

Tools:

Flathead screw driver

Applicable Models:

Mercedes-Benz 300CE (1990-93)
Mercedes-Benz 300E (1990-93)
Mercedes-Benz 300TE (1989-92)
Mercedes-Benz E320 (1994-95)

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.

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.

Remember to clear the codes once you have installed a new sensor.

The MAF sensor (red arrow) is located between the air filter (yellow arrow) and the intake tube (green arrow).
Figure 1

The MAF sensor (red arrow) is located between the air filter (yellow arrow) and the intake tube (green arrow).

The sensor comes complete with the plastic tube it is housed in.
Figure 2

The sensor comes complete with the plastic tube it is housed in. While you can remove the sensor to attempt to clean it, if you are replacing the MAF it will arrive already in the tube. The MAF is held in place by two clips to the air filter box (red arrow, one shown, one below) a single clamp to the intake tube (yellow arrow) and the wiring harness (green arrow).

Turn the locking ring on the harness (red arrow) counter clockwise; this will separate it from the connection on the MAF (yellow arrow).
Figure 3

Turn the locking ring on the harness (red arrow) counter clockwise; this will separate it from the connection on the MAF (yellow arrow).

Separate it from the air filter lid by pulling back on the two clips (red arrows).
Figure 4

Separate it from the air filter lid by pulling back on the two clips (red arrows). 

Use a flathead screwdriver and unscrew the clamp to the intake tube (red arrow).
Figure 5

Use a flathead screwdriver and unscrew the clamp to the intake tube (red arrow).

Push the MAF back on the plastic bellows connecting it to the intake tube (red arrow).
Figure 6

Push the MAF back on the plastic bellows connecting it to the intake tube (red arrow). This will allow you to remove it from the air filter lid.

Next slide it out from the bellows on the intake tube.
Figure 7

Next slide it out from the bellows on the intake tube. This will free the MAF and housing from the vehicle (red arrow). When you order a new MAF this piece is what you will receive.

You can attempt to clean the MAF with MAF cleaner.
Figure 8

You can attempt to clean the MAF with MAF cleaner. Most people have received only moderate success with cleaning the MAF but it is an expensive part so you may want to try that first. If you attempt to clean the MAF do not use anything but MAF cleaner and never touch the sensor (red arrow) with your hands or anything metal. Installation is the reverse of removal.

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Comments and Suggestions:
brabus Comments: Hi.im having trouble with my w210 e320 with the m104 i6 engine.it starts and dies instantly.so i took it to a repairshop and was told that i needed a mass airflow sensor.so i went and bought one only to be told that the one i bought is for a 270 cdi.my question is can a MAF of a diesel work on a petrol?thanks
May 9, 2016
  Followup from the Pelican Staff: I don't believe so. I think the part is different. Give our parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
Billy Comments: I have just replaced my air mass sensor. My car exhaust smells very strong and poor fuel consumption. Could it be that my air/fuel mixture is bad. What is the ideal co reading that it should be and what other possible symtoms could it be?
December 14, 2015
  Followup from the Pelican Staff: co 0.5% - Nick at Pelican Parts  

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