Driving along today no problem then suddenly a misfire and the engine warning light starts flashing. Nursed it home and discovered that the light illuminates when you press the throttle and goes out when u leave it. Replaced plugs but no difference , engine will idle ok for so long then starts to mis, If I hold the engine at any revs its ok but if a blip the throttle it misfires. Any ideas before Vauxhall get it ? D