white smoke and very lumpy idle

Hi all new to the forum ive got a 98disco1 300tdi recently i put sum old diesel from a can into my tank ever since its been a pain to start you have to give it lots of gas and when it does start it sounds like its running on 3cylinders and vibrates like mad when warm its a lot better it also has a lot of white smoke until warm it feels like its struggling to get fuel ive changed fuel filter and still no different. Going to have injectors tested tomorrow any ideas greatly appreciated many thanks elliott