The MAF Sensor measures the flow rate of
the air the enters the M5 (e39)'s plenum. The rate of flow that the MAF
Sensor measured is then communicated to the ECU (DME), which in turn
determines how much fuel needs to be injected into each of the 8
cylinders. A faulty MAF Sensor will cause your M5 (e39) to exhibit
MAFS (Mass Air Flow Sensors) seem to
begin to fail between 30,000 to 60,000 miles on the M5 (e39). The MAF
Sensors fail because dirt and oily substances get baked onto them over
time. Failing MAF Sensors will cause the M5 (e39) to exhibit intermittent
problems such as a rough idle and power-loss. Some M5 (e39) owners have
literally felt that their car became noticeably more powerful after
installing new MAF Sensors. These owners probably had deteriorating MAFS
for a while, and did not notice the slow reduction in performance, until
the MAF Sensors failed completely, or were near the point of complete
Sometimes the SES (Service Engine Soon or
Check Engine Light) will light-up and a MAF Sensor error code will
register (this can be checked with a code reader or by your technician).
However, small amounts of impurities can collect on the MAF Sensors over
time which can lead to drivability problems before the MAF Sensor is dirty
enough to cause the SES light to come on. Replacing the worn MAF Sensors
with new MAF Sensors can make your M5 (e39) drive like it should.
If one has to change their M5 (e39) MAF
Sensors, one can simply visit their local BMW dealer and pay close to
$1,000 for new MAF Sensors (housings and installation included). However,
there is a much less expensive alternative, which is to purchase the kit
that we are offering for sale here.
Remember that you will need 2 MAF
Sensors. The BMW replacement part includes the MAF Sensor housing, which
does not need to be replaced. All you need to replace is the sensor within
Some M5 (e39) owners have tried to clean
their MAF Sensors, however, this has not been successful, with most seeing
better performance for only a few days. Replacing the old MAF Sensors with
new MAF Sensors is the only effective solution.