Hi, we have a 2002 Fiesta 1.4 tdci diesel with 88k on the clock. It has become difficult to start on cold mornings and cuts out if we lifts off before it warms up. It is very sluggish in acceleration and will not drive at more than 70 mph. It has been checked on several different diagnostic systems yet does not return any fault codes (only checked when warm engine). When trying to start from cold it emits a cloud of grey/ white smoke while turning over and makes a lumpy, banging noise before eventually catching on and firing up. More difficult to start when very cold or fuel tank is below quarter full. Once it is warmed up it starts much easier, but the power output is very sluggish. No acceleration for overtaking and crawls up hills with foot flat on the floor. Air bubbles are visible in the fuel line. Patchy service history so don't know when fuel or air filters etc. last changed. Dual mass flywheel and clutch and cambelt recently replaced. All the suggestions so far are very expensive and don't guarantee to fix the problem. Any ideas please? Thanks. Pete, Southampton.