ME-SFI idling speed control - function - GF07.61-P-2007SM

ENGINE 113.986

ENGINE 113.987

ENGINE 113.988

ENGINE 113.989

Fig 1: ME-SFI Idling Speed Control - Function

Courtesy of MERCEDES-BENZ USA

The throttle valve actuator (M16/6) controls the idling speed by altering the position of the throttle valve. It is actuated by the engine electronics control unit (N3/10).

To assist the idling speed control, the ignition angle can be "retarded" by as much as 20° crank angle and "advanced" by as much as 20° crank angle.

The ME-SFI [ME] control unit () controls the idle speed with different engine loads (e.g. drive position engaged, refrigerant compressor (A9) activated) according to the input signals.

Warm-up phase (heating speed)

In order to bring the catalytic converters more rapidly up to operating temperature the engine speed is raised to 1100 rpm to 1300 rpm:

at coolant temperatures < 40°C,
after each starting procedure,
when the engine is idling.
for about 20 seconds

Once this time has elapsed, the idling speed in increased at a coolant temperature < 70°C, depending on the temperature, for about 50 seconds by around 50 to 100 rpm.

Automatic transmission

When a drive position is engaged, a lower engine speed is controlled in order to reduce the creeping tendency of the vehicle.

The information "Drive position engaged/not engaged" is transmitted by the ETC [EGS] control unit (N15/3) to the ME-SFI [ME] control unit.

Refrigerant compressor

Before switching on the refrigerant compressor, the AAC control and operating unit (N22) sends a signal (via the CAN databus) to the ME-SFI [ME] control unit to prevent a fall in the rpm at idling speed as the refrigerant compressor is being switched in. The ME-SFI [ME] control unit responds by increasing the opening angle of the throttle valve.

Adjusting the ignition angle enables a faster response than adjusting the throttle valve.

The idle speed can be influenced with the STAR DIAGNOSIS.

Component description for the crankshaft position sensor	L5	GF07.04-P-6010SM
Component description for the coolant temperature sensor	B11/4	GF07.04-P-6040SM
Component description for the ME-SFI [ME] control unit	N3/10	GF07.61-P-6000SM
Component description of ignition coil	T1/1-T1/8	GF15.10-P-2100SM
Component description for the accelerator pedal sensor	B37	GF30.20-P-2010SM
Component description of throttle valve actuator	M16/6	GF30.20-P-2020SM