GF07.61-P-2007AMG ME-SFI Idle Speed Control, Function

GF07.61-P-2007AMG ME-SFI Idle Speed Control, Function







Throttle valve actuators regulate the idle speed by altering the valve actuator positions. Actuation is by the ME-SFI [ME] control unit. To assist idle speed control, the ignition angle can be retarded by as much as a 36° crank angle and advanced by as much as a 20° crank angle.

The ME-SFI [ME] control unit controls the idle speed according to the input signals:
- At different engine loads, e.g. steering turned to full lock (power steering pump), drive position engaged, refrigerant compressor (A9) engaged)
- In the warming-up phase
- For an on-board electrical system undervoltage
- At different mixture compositions e.g. via lambda control or fuel evaporation control system.

Warm-up phase (heating speed)
The idle speed is raised to 1100 to 1300 rpm for about 20 seconds, in order to bring catalytic converters more rapidly up to operating temperature if:
- The coolant temperature is <40 °C after the starting procedure
- Engine at idle

After this time has elapsed and at a coolant temperature of < 70 °C, the idle speed in increased by around 50 to 100 rpm (depending on the coolant temperature) for about 50 seconds.

Automatic transmission
When a drive position is engaged, a lower idle speed is controlled in order to reduce the creeping tendency of the vehicle. The information "drive position engaged or not engaged" is transferred via the CAN data bus from the Electric controller unit (VGS).

Refrigerant compressor (A9)
To avoid engine speed dropping in the idle speed range when the refrigerant compressor is engaged, the AAC [KLA] control system issues a signal to the ME-SFI [ME] control unit via the CAN data bus, which is adapted appropriately to the idle speed (increased).

If the air conditioning is switched on and the drive position engaged (dependent on the outside temperature), the idle speed is increased by about 100 rpm.

Undervoltage in the on-board electrical system
If the ME-SFI [ME] control unit detects an undervoltage, the idle speed is increased for the engaged drive position by about 100 rpm.

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

The idle speed can be influenced (preset) using STAR DIAGNOSIS.