Offroad-Express

hey all, can anyone tell me if you need to
have an oxygen sensor and what it is that it
does.It is not connected at the mo and is on
a 1989 ecudo
cheers Al

as far as i understand when the computer is in closed loop mode it uses the O2 sensor to fine tune the fuel injectors to get the right air/fuel ratio. so you will be running slightly rich and use a bit more fuel with it disconnected.