My W reg Zafira has had light-throttle jerkiness for a while and it gets worse as a yearly service draws closer. Last year they 'cleaned out the throttle body' and it cured the problem. The cleaning was just a carb cleaner spray! This year, the jerkiness reappeared and the throttle body re-cleaned. This time there was no cure. Given this I decided to have a go myself after reading about Vectra ECOTEC cam cover breathing pipe problems. Off came the air filter to throttle body ducting. I disconnected the throttle cable to throttle body to get better access to the 2 cam cover breather hoses that join onto the throttle body. The upper one vents up stream of the throttle and was not blocked. The lower hose (which vents downstream of the throttle and is thus more 'active' on light throttle) was removed and dry dust came out! Using a mirror and torch allowed me to that a small hole in the throttle body was blocked. With my trusty paper clip, that had just flashed out my self made EGR error code (see other posting), I opened up the small hole. Subsequent journeys have had no 'jerkiness', although early days yet! HTHs.
