sorry to hear the problems you are having with your scenic. You do not mention what engine yours has fitted but I am assuming its a 1.6 16v VVT
. If the emissions light is coming on does it come on all the time or intermitantly and how is the car running. You mention the coils
and plugs have been replaced so its not that. It could be a whole list of things. Has the car been to a Renault dealer and had a clip diagnostics done to try and find out what the fault is.