Idle Speed Control

OPERATION
The idle speed is kept constant by an idle speed actuator which supplies the engine with the necessary amount of air. The control is effective as soon as the Digital Motor Electronic (DME) control unit detects the idle speed position by way of the throttle switch or the throttle potentiometer. The preprogrammed engine speed values in the DME control unit are compared with the actual values and corrected. In this way, deviations in engine speed due to mechanical wear, leakages or different functional resistances offered by the engine are compensated. This therefore renders adjustment of the idle speed unnecessary.

Vehicles with Air Conditioner System
On models equipped with an air conditioning system, the idle speed is increased after the system detects that the air conditioner has been switched on. After detecting the A/C compressor signal, the air required at idle speed is corrected to the optimum value.

Vehicles with Automatic Transmission
In the case of vehicles equipped with Electronic Transmission Control (EGS), on detecting the engaged drive range (1, 2, 3 or D), the amount of idle air is increased by the idle speed actuator in order to compensate for a drop in the engine speed caused by the torque converter. However, the nominal speed is set slightly lower.