We have a petrol driven 2003 Vauxhall Zafira that has started to have an intermittent starting problem. What happens is that sometimes there is no problem in starting and running, while at other times it fails to start (it does turn over), and if it does catch it sounds like it is running on 2 or 3 cylinders, and stalls when any load is placed on it. It has been into a garage twice, once to replace the throttle unit, and once to clear out some air intakes, but still the problem persists.

Anybody got any thoughts before we throw yet more money at it?