Heating problem

[geebee]

I have 320i coupe manual 1995. My problem is this....when I turn on the air recirculating switch on the heater/A/C control the idle goes up to 2000rpm then as soon as i press the throttle and release it, it starts to fluctuate from 1500 to 2000 rpm continuously. I disconnected the compressor, no difference !The aircon works ok, so does the heater....just does not like the recirculate button on. Changed the heater/A/C control (rotary type) still the same. Any help will be appreciated