FORD MONDEO 02 dura torqu tddi smokes alot on start?

hi there
On cold start the engine smokes alot and makes knocking noise's
the smoke is a light colour with tint of blue.
once the engine is warm its fine and runing smooth, no smoke but a slight kocking noise on excelleration still remains.
i have shown to loads of different experts and they are all giving me different views.
can you please help me.