how can i fix my car missfire on a vauxhall vectra 1.8 petrol?

if it was running ok previous i assume you replaced spark plugs if so try to identify which cylinder is giving you a prob by using a set of insulated pliers and while engine is running follow the leads back to the coil pack/packs and unplug slightly 1 at a time you should notice a fat spark if so then pull it further away until no spark and listen to the engine for a difference in running if no difference in running but getting spark then problem either lead plug or at worst engine if no spark then prob maybe coil pack/packs....... if coil pack ok for all then try spare spark plug which you may have changed in other end of ignition lead earthing the plugg to a metal engine part if no spark at plug maybe lead if sparks check replaced plug or change back for old proven one if that does not cure prob maybe involve engine issue hope this helps

keith
October 2010