mrm629

Hey guys, I've got a 2002 E46 330ci auto transmission, and when i put it in gear(reverse or drive), the rev drops to like 500RPM or slightly lower and then comes back up to about 600-650RPM, causing the car to vibrate while low. When the aircon is turned on, the RPM is slightly higher, maybe by 50RPM but when i shift it to drive or neutral, it does the same thing. Also, the aircon gives off a whistling/humming sound. Has anyone else faced this issue? Would it be the idle RPM settings?