Help!!!!! Ford taurus!!!!!!!!!!

This is my friends car. I forget if it was a 92 or a 94. When you start it it idles rough. Its gooes up down up down up down and the lights obviously dim and brighten with the rpm difference. Then when you put it into reverse it will stall unless you neutral drop. Somtimes it grinds in reverse to. Any Ideas?

Might look around the engine for a vacuum leak of some sort. Maybe a hose came loose or is cracked. Sometimes you can hear them hissing before you see them. I have had some cars that behaved similar with a vacuum leak. Usually the gas mileage drops off too. Could be a farily major leak or more than one. If you could find it, you might be able to just reconnect it or wrap some duct tape around it.