Fuel Metering; Air Intake - BMW 1999-2005 M3 Service Manual

Engine-General
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Fuel purge valve and fuel tank
leakage diagnosis pump (LDP or
DM-TL).
Fuel metering: The ECM meters
pressurized fuel by changing the
opening time (pulse width) of the fuel
injectors. The exact amount of fuel
injected is determined by the amount of
time the injectors are open. To ensure
that injector pulse width is the only factor
that determines fuel metering, fuel pump
pressure is maintained by a pressure
regulator. The injectors are mounted to a
common fuel rail.
The ECM monitors engine operating
conditions to determine injector opening
duration. Each injector can be
individually controlled for cylinder
selective fuel trim. The fuel-injectors
inject fuel at an angle in a dual cone
spray pattern.
Air intake: Air entering the engine passes
through a pleated paper air filter in the
air cleaner. Intake air mass is then
measured by a mass air flow (MAF)
sensor. A reference current is used to
heat a thin film in the sensor when the
engine is running. The current needed to
hold the temperature of the film constant
is the basis of the electronically
converted voltage measurement
corresponding to the mass of the intake
air.
Idle speed control: Idle speed is
electronically controlled via the idle
speed control valve by bypassing
varying amounts of air around the closed
throttle valve. Idle speed is not
adjustable. The ECM determines idle
speed by controlling a dual-winding
rotary idle control valve. The basic
functions and parameters of idle speed
control are as follows:
2/25/2009 9:58 PM