hi whilst driving today i had a 4 to 5 times misfire going down the road,people where diving for cover

.anyway van cut out and i had to pull over.anyway what it is every time i go over a high,ish speed bump or say i am parked half on/off a highish curb and bump off the rotor arm seems to unseat its self and seats itself the wrong way round.is this a common problem do i need a new rotor arm/dizzy?cheers dave.1.9dg petrol engine
