Idle Speed; Oxygen Sensors - BMW 1999-2005 M3 Service Manual

Maintenance
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Similarly, turn main engine drive
belt tensioner lug (B) clockwise
and remove belt.
WARNING!
Observe care when replacing belts.
Personal injury could result if a
tensioner springs back into position
uncontrollably.
CAUTION!
Mark drive belt rotation direction if
removing and reusing an old belt.
- When installing a new belt, gently
pry it over the pulleys. Too much
force may damage the belt or the
accessory.

Idle speed

Engine idle speed can change due to a
number of factors, including normal
wear. The idle speed in E46 models is
electronically adaptive and
non-adjustable. See
Injection for more information.

Oxygen sensors

The engine management system in
E46 models is equipped with multiple
oxygen sensors. A regulating sensor is
mounted before each catalytic
converter and a monitoring sensor
downstream of each converter. The
regulating sensor monitors engine
combustion efficiency and helps to
control the fuel injection system and
exhaust emissions. The monitoring
sensor is used by the on-board
diagnostic (OBD II) system to monitor
the function of the catalytic converter.
130 Fuel
2/25/2009 10:03 PM