After filling my Hyundai Trajet GSI TD with fuel, the car will not start after parking on any lenght of journey, have to wait up 2 hrs before it will start again, missfires while driving and cuts out at round about, the malfunction indication light is on, which the book says is a malfunction of an exaust gas related component, my mechanic has put on diagnostic machine, comes up with cam shaft sensor, which has been changed twice now but not fixed the problem, i'm very worried about driving it as i could have an accident with it cutting out. could it be the charcoal vapour canister. please can you help,