Hi all, I would like to know if its possible to adjust my idling so that my car does not shake when i put on AC?

I discovered that my car idles at 5 on the rev counter.but when i put on the ac ,it drops further. when i press my gas pedal slightly the car stops shivering when the rev counter gets to 10. So my questiion really is how can i adjust my idling rate to idle the car at 10 permanently so my car stops shivering violently?

I wld like to do this myself so i can note where i started from and put things back to the way they were before i started . I wont like any other person to do this for me. Also because I used to do this on my Golf MKII (carburettor engine though).

Thanks all

__________________
1986 230E (revisions on the way)