How do you adjust the idle on a Volvo?

I'm not sure what year or model of the car but if its somewhat new meaning about 1994. Then the computer does it and there is no adjustment. If you getting a rough or low idle it is probably time for a tune-up. If tune-up doesn't work you may have to replace idle control valve, up to 1989 there was an idle adjustment knob on throtle body for fine tunning.