Do you have to change O2 sensors ?

how many do I need  on a 2.8 v6 

cars done 100k 

runs ok 

but lumpy of take off

done plugs 

just needs good service I think 

There are 4 Lambda sensors, you would normally only replace them if there was a fault code indicating a problem with one or more of them or the car failed the MOT for emissions but again chances are there would of been a warning code set 

ok thank you   for reply