My 2002 Mini runs great all 99% of the time but has two quirks that I was curious if all R50s do it. Before you say it...it already has a new O2 sensor and no fault codes.
When it is cold outside the car idles like crap for the first few minutes but now that it's warm, I was reminded how poorly it idles with the A/C on. It shakes and often stalls when stopping or at a parked idle. Remind you...only when the A/C is on and not every time. No air-it starts, runs and drives flawlessly.

So is this just the way they are?

 

Try resetting your ECU. Just a thought.

 

Mine has always been this way. The A/C is truly a power suck when it comes to these cars.

 

I don't have the problem, mine idles at around 900 rpm without air, when air is on rpm's increase to about 1100

 

Mine acts normal with the AC on....of course the standard lack of power is there but no attempted stalls.

 

Check to make sure your electric fan comes on when the A/C is turned on. If it doesn't the pressures through the condensor and the compressor are wrong. This puts extra load on the engine when the compressor clutch engages...
Kaveman

 

Already did the reset which does do wonders, just not not for this issue. And yes the fan does come on. A/C pressures are right on the money.
It just seems like the ECU programming sucks, almost like the idle correction doesn't happen until after the load is placed on the motor instead of increasing the idle at the same that the compressor and fan comes in.

 

I got to thinking about your problem and I wonder if you have a clogged fuel filter? It supplies enough fuel at idle and when a bigger (read acceleration) is put on it but not enough when the A/C kicks in. I'm thinking out loud. I keep running it through my head to see if that makes sense but I have not decided yet.

 

Doubt it's fuel filter. Pump pressure does not change so a blocked filter is a blocked filter. Like the idea of an EMU reset to fix. I will try it with my two.