Idle Speed/Throttle Actuator - Electronic: Description and Operation

Idle Speed Control

Idle Speed is controlled by the EMS2000 and EDR without the aid of an idle speed motor. For smooth driveability of the vehicle, the engine speed should remain constant when at idle no matter what the varying loads may be on the engine. The driver should not detect a fluctuation in engine idle speed under the following conditions:

- Engine cold start (increase in idle speed setting).
- Switching of different electrical loads (e.g. headlights, HRW or HFS).
- Turning the steering wheel to full lock (increased load from the Electro Hydraulic Power Steering (EHPS pump).
- Air Conditioning Compressor engagement.

When there is a rapid change in electrical power demand on the alternator ie. front and rear heated windshield on with air conditioning fully on, there will be a corresponding rapid increase in the mechanical loading that the alternator exerts upon the engine. This in turn will have a significant effect on the engine idle speed stability. There is a delay between the electrical demand being made on the alternator and the mechanical demand being made on the engine. During this period of time the alternator transmits a signal to the EMS2000 to inform the control unit of the change in electrical load. The signal is PWM and allows the EMS2000 to control the throttle demand at idle to prevent flares and dips in the engine speed due to alternator loading or unloading.

The target idle speed setting for all MINI models is 750 rpm.


Idle Speed "Jack" Feature
As part of the vehicle power balancing strategy there is a feature to increase the engine idle speed to a set point when the EMS2000 system voltage reaches a certain threshold. The engine speed will remain at this point for a period of time before returning to the normal set point when the system voltage has recovered.

EML Warning LED
If the EMS2000 detects an engine safety related fault (but is not emissions related) in the EMS2000 itself, the EML warning light will illuminate in the IKE to show there is a fault with the drive by wire system. (This could be caused by a faulty throttle motor, gearbox or a sticking throttle flap.) The Warning Led is amber in color and is activated through a CAN Bus message to the IKE.