The ME range allows several methods of idle control. Closed Loop, Open Loop and a ‘fixed’ idle duty are all achievable with the ME system. Spark Scatter can also be used for further fine tuning of idle.


If you are using a Plug-In ECU, the suitable OEM calibration file should contain tried and tested idle control settings to deliver as close to (and in some cases exceeding) OEM performance and response.


You may have had the throttle ‘jacked’ open mechanically to aid in startup and VE tuning, it is now a case of mechanically reducing this idle such that when the engine is warm it indeed idles at your target warm idle speed, even with Idle air control bypass unplugged/blocked.


Your engine should be set to mechanically idle well, and all sites around idle in the VE/Ignition table be tuned accurately.


Idle control can't stop an unsteady system from being unsteady. 


If your engine will not remain at a steady idle speed on a throttle stop, then you have basic tuning issues which need to be remedied first. Yes, it may not be able to compensate for sudden electrical/AC/Power Steering loads etc, but in a steady state condition, it should stay steady state.


Note that the ME221 does not support stepper based idle motors, only the more common PWM bypass type. The ME442 supports stepper based idle also, as well as Drive-by-Wire idle control.


The idle settings are exhaustive - OEM idle (and sometimes even better) on a correctly tuned ME ECU is more than achievable: