Hi I,m working on a TD5 that has developed a missfire, No eml or reported dtc,s other than a P0120 throtle position fault. I have removed and replaced injectors 2 and 4 and when rebuilt the engine ran smoothly for a while. There is an extensive carbon deposit in the fuel tank but this is firmly attached to the sides of the tank and not in suspension in the fuel. When the engine is running the exhaust is smokey and smells of unburned fuel, any one experianced this before?