Tlaidler

HI guys just signed up today as have a problem with car mentioned above. Basically the car misfires and judders and doesn't pull at all when it's doing it and its also intermittent, can go for a few weeks without doing it then will suddenly start playing up :( I've had it plugged in and no faults are recorded tbh I've no idea why its doing it. I've changed the fuel filter but still no joy Does anyone have any suggestions? Thanks in advance