Solution: the evaporator drain line is plugged. All A/C systems dehumidify as well as cool so the water collected by the evaporator has to drain off. The drain line is on the passenger side coming down out of the firewall. Normally you should see drips of water onto the pavement from that side if the drain is working. If no drip you'll have to get under there and see what's going on.

High idle? How high? When the A/C is on you'll see the idle boost up slightly, perhaps about 200 RPM but no more.

1998 Sportage - Gone.
2004 Honda Civic Coupe.
2007 Suzuki Grand Vitara - She got it.