Vauxhall Vectra engine idling problem

replace the cap rotor arm and leads and plugs and this should resolve the miss fire problem the reason is have said these is juxt to save you the hassle of running to and from the shop so do them all and problem solved but dont play with the fuel rail cap as its high pressure and would be dangerous and i wouldnt say that its a fuel problem but it will say its electrical

there are modified idle air control valves for these vehicles and an engine breather modification and also a software update for the engine control unit, these parts and update are dealer only, also the cap you refer to is just a service port for allowing fuel pressure to be checked. These cars from cold do sound a little loud for a couple of minutes on start up because of the secondary air pump running.