megane 1600 2002?

cam belt and pulley was changed at 63,000 oct 08 . In april 2009 I start it from cold was ok but then leave for a few hours starts and dies will not keep running if you try throttle it dies quicker will not run I have to keep trying to start it and let it do its own thing and eventually runs. Took to renault garange said it is the suspention pulley which they changed at cost of 300-00 only for it not to work they then said they had found another fault a sensor so I told them that I was not paying any more they changed the sensor in the bottom of engine . It fixed it but almost a year later it is starting again Has anyone any idea before I try to get it sorted again help please.