1998 Renault Kangoo 1.9d misfire and white smoke

Hi people, I have recently purchased a low mileage 1998 renault kangoo 1.9d van as a run around. I bought it knowing there was an issue with a misfire and upon viewing the van noticed airbubbles in the fuel line... So i took a risk and bought it and changed the fuel filter right away! Now theres no more air bubbles in the fuel line however im still getting a misfire when approching junctions. If i put my foot down and rev the engine hard i get loads of white smoke (smells of unburnt fuel) and then it clears and the van goes fine..ish again. Any help and advice will be greatly appreciated :)