i really dont know what the cause is but it kept happein to my peugeot 202 a couple of years ago, I replaced a sensor with no luck. adding holts injector cleaner or engine cleaner to the petrol really helped in the short trm but nothing else worked. the problem eentually cleared up on it own (after about eighteen months), watch out because ikepton bump starting it when it cut out and ended up waringout my clutch. good luck
kevin, February 2008