misfire mk1

Hi everyone im new to the site and in desperate need of your help my dad has a mk1 1.8 gti j plate rivage cabby which has a slight misfire all the time
as soon as you start it it will tick over as it should but if you blip the throttle it misfires through the rev range if you take the revs up slowly it seems to be ok same when you drive it just as soon as you go to accelarate away hard it misfires
if you guys or girls could shed any light on this i would be so gratefull thanks in advance rob

hi . if you check distributor make sure no dampnes inside the cap.
 also check you have not a faulty lead .try that if no succes let us know and will try help you out

thankyou will try this tommorow and see how i get on