hi there, i have a 94 ed falcon that seems to have a slight flat spot just off idle and only when cold, the car also seems to be using a fair bit of fuel and i was wondering if the oxygen sensor could be a bit crook , do these sensors have a life span? if so how can you test them to see if they are still ok?, they dont seem that expensive and the car has 220,000 on the clock so maybe it is due, any other tips appreciated

Depends on how much more fuel you are using,i would check your thermostat.It maybe staying open.Would check your timing and your plugs and also carry out a cooling system pressure test.You might be leaking coolant into your combustion areas.That maybe your slight flat spot when cold,then when your car warms up it is fine cause that bit of water leaking will burn up.