hey 89 Gx maybe i'm not saying this right,what I mean is the compressor cycles on and off on the heat side,I don't mean it's is running the A/C,
and you'll notice below 9 deg Celsius that your compressor won't cycle in and out and your compressor is basically a pulley then.
That's what tweaked me to the rough idle,went away when it was below 9 deg.
Hope you can understand all that.
getting tired of typing,have a good one.