Intake Air Flow Control

Under certain engine parameters, the MDK throttle control and the idle speed actuator (ZWD) are operated simultaneously.

The ECM detects the driver's wish from the twin potentiometers monitoring the cable/pulley position.

This value is added to the idle speed control value and the total is what the ECM uses for MDK activation. The ECM then controls the idle speed actuator to satisfy the idle air "fill", in addition, the MDK will also be activated = pre-control idle air charge. Both of these functions are utilized to maintain idle RPM.

The MDK is electrically held at the idle speed position, and all of the intake air is drawn through the idle speed actuator. Without a load placed on the engine (<15% load), the MDK will not open until the extreme upper RPM range.

If the engine is under load (> 15%), the idle speed actuator is open and the MDK will also open.

In the upper PWG range (approximately > 60%), the MDK is switched off. The throttle valve is opened wider exclusively by the pulley via the spring linkage.

At the full throttle position, "kickdown" is obtained by depressing the accelerator pedal fully. This will overwind the pulley, but the spring linkage will not move the throttle plate past 90 degrees of rotation.


NOTE: If the MDK is defective, it is replaced as a unit and is not internally serviceable.