ME-SFI idle speed control, function - GF30.22-P-0003V

ENGINE 272.920 in MODEL 203 up to Model Year 8 

ENGINE 272.922 in MODEL 211 

ENGINE 272.940 in MODEL 203 up to Model Year 8 

ENGINE 272.941 in MODEL 203 up to Model Year 8 

ENGINE 272.942 in MODEL 171 up to Model Year 8 

ENGINE 272.943 in MODEL 211, 219 

ENGINE 272.944 in MODEL 211 

ENGINE 272.945 in MODEL 251 up to Model Year 8 

ENGINE 272.946 in MODEL 221 up to Model Year 8 

ENGINE 272.960 in MODEL 203 up to Model Year 8 

ENGINE 272.963 in MODEL 171 up to Model Year 8 

ENGINE 272.964 in MODEL 211, 219 

ENGINE 272.965 in MODEL 221 up to Model Year 8 

ENGINE 272.966 in MODEL 230 up to Model Year 8 

ENGINE 272.967 in MODEL 164, 251 up to Model Year 8 

ENGINE 272.970 in MODEL 203 up to Model Year 8 

ENGINE 272.972 in MODEL 211 

ENGINE 272.975 in MODEL 221 up to Model Year 8 

ENGINE 273.922 in MODEL 221 up to Model Year 8 

ENGINE 273.923 in MODEL 164 up to Model Year 8 

ENGINE 273.924 in MODEL 221 up to Model Year 8 

ENGINE 273.960 in MODEL 211, 219 

ENGINE 273.961 in MODEL 216, 221 up to Model Year 8 

ENGINE 273.962 in MODEL 211 

ENGINE 273.963 in MODEL 164, 251 up to Model Year 8 

ENGINE 273.965 in MODEL 230 up to Model Year 8 

ENGINE 273.967 in MODEL 209 

ENGINE 273.968 in MODEL 221 up to Model Year 8 

ENGINE 272.940 in MODEL 209 

ENGINE 272.960 in MODEL 209 

Shown on engine 272.963 in model 171 

Fig 1: ME-SFI Idle Speed Control Function Diagram

Courtesy of MERCEDES-BENZ USA

The throttle valve actuator controls the idle speed by altering the position of the throttle valve. It is actuated by the ME-SFI control unit.

To assist the idle speed control, the ignition angle can be retarded by as much as 36° crank angle and advanced by as much as a 20° crank angle.

The ME control unit actuates the throttle valve motor in line with the input signals received at the ME control unit.

The throttle valve actuator controls the idle speed:

• At different engine loads, e.g. steering turned to full lock (power steering pump), drive position engaged, clutch pedal actuated, refrigerant compressor engaged
• In the warming-up phase
• At undervoltage
• At different mixture composition e.g. through lambda control or fuel evaporation control system.

Heating-up speed 

In order to warm up the catalytic converters more rapidly to operating temperature, the engine speed is increased in the idle speed range to 1100 up to 1300 RPM for about 20 seconds after each starting procedure at coolant temperatures of < 40°C. Following this period, the idle speed is increased at a coolant temperature < 70°C for around 50 seconds by approx. 50 to 100/ RPM. When a drive position is selected, this is immediately reduced.

Automatic transmission (AT) 

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 transmission control unit via the CAN data bus to the ME control unit.

AC compressor 

To avoid engine speed dropping in the idle speed range when the AC compressor is engaged, the automatic air conditioning control system issues a signal to the ME control unit via the CAN data bus which is adapted appropriately to the idle speed (increased).

When the air conditioning unit is switched on and the external temperature exceeds 35°C, the idling speed is increased for the driving mode selected by about 100 RPM when the switch-on threshold of about 900 RPM is exceeded. This increase is canceled again when the external temperature drops below 32° C.

Undervoltage 

If the engine control unit detects an undervoltage the idling speed is increased until the ignition is switched off for the driving mode selected by about 100 RPM.