ME-SFI idle speed control, function - GF07.61-P-2007CY

ENGINES 272.911 in MODEL 204.0 up to Model Year 08/Modification Year 07 

ENGINES 272.921 in MODEL 204.0/2 up to Model Year 08/Modification Year 07 

ENGINES 272.947 in MODEL 204.0/2 up to Model Year 08/Modification Year 07 

ENGINES 272.948 in MODEL 204.0 up to Model Year 08/Modification Year 07 

ENGINES 272.961 in MODEL 204.0/2 up to Model Year 08/Modification Year 07 

ENGINES 272.971 in MODEL 204.0 up to Model Year 08/Modification Year 07 

The throttle valve actuator (M16/6) regulates the idle speed by adjusting the throttle valve position. It is actuated by the motor electronics control unit (N3/10).

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.

Corresponding to its input signals the ME-SFI [ME] control unit controls the idle speed in the warm-up phase and for different engine loads (e.g. gear range engaged, A/C compressor (A9) switched on).

Warm-up phase (heating speed) 

In order to bring the catalytic converters to operating temperature more quickly, the idle speed is raised to approx.1100 to 1300 rpm for approx. 20 seconds if:

• Coolant temperature <40°C
• Engine start has occurred

After this time elapsed, the idle speed is increased at a coolant temperature <70°C depending on the temperature for about 50 seconds by about 50 to 100 rpm.

The increase will be canceled when a gear range is engaged.

with automatic transmission 722.9 

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

The information "Gear range engaged" is conveyed to the ME-SFI [ME] control unit via the drive train CAN (CAN C) by the electronic selector lever module control unit (N15/5).

For manual transmission 716.6 

When actuating the clutch pedal the idle speed is stabilized. The operation of the clutch pedal is detected by the ME-SFI [ME} control unit through the clutch pedal switch (S40/3).

Refrigerant compressor (A9) 

So that at idle the engine speed does not drop when the A/C compressor is switched on, the automatic air conditioning control and operating unit (N22/7) transmits a signal to the ME-SFI [ME} control unit via the interior CAN (CAN B) and chassis CAN (CAN E) before the A/C compressor is switched on. This responds by adjusting the idle speed appropriately.

Undervoltage of on-board electrical system battery (G1) 

If the ME-SFI [ME] control unit detects an undervoltage, the idle speed is increased until the ignition is switched off for the driving mode selected at around 100 rpm.

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

The basic setting of idle speed can be influenced with the DAS [Diagnosis Assistance System]

	Electrical function schematic for idle speed control			PE07.61-P-2754-99FAB
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