AC causes low idle / stall

I'm driving my sister's car while she is in California since it gets twice the fuel mileage that my truck does. 1993 Toyota Celica GT with a manual transmission that runs great, except when the AC is turned on. Engaging the AC causes the car to idle very low (200-400 RPM), which pretty much stalls the car. If the AC is turned off, the RPMs jump back up to normal. I have posted this in the Toyota section, but there's not much activity over there and I assume the problem would be the same whether it's a car / truck of almost any make. Maybe the AC relay is not sending a signal to the computer to add more throttle when the AC is engaged? Seems like a simply fix, just can't put my hands on it right now. Thanks for any help, its nice to have AC in Georgia during the summer months.

A buddy of mine had the same issue on a Camry (sp ?) and the shop I sent him to clean the TB and problem solved.

//2000CAYukon

I've seen that on a couple toyotas, the IAC being bad or carboned up will cause it too.... cleaning it is implied with cleaning the throttle body, but I just wanted to add that.