Idle Speed Control (Linkage): Description and Operation

GF07.16-P-3002IC CDI Idle Speed Control, Function

Component Identification:

Idle speed control keeps the idle speed constant, even during load requests, such as drive position selected (with automatic transmission) or when coolant compressor is switched on (A9).

For this purpose, the CDI control unit calculates the target engine speed and performs a target-actual value comparison. Accordingly, the CDI control unit controls the rail pressure via the quantity control valve and the pressure regulator valve and controls injection timing via the fuel injectors.
Rail pressure and injection time determine the quantity of fuel injected.

The following input signals are evaluated by the CDI control unit for idle speed control:
^ Engine speed
^ Coolant temperature
^ Accelerator pedal position
^ Rail pressure