As I used to work in a ford main dealer in Birmingham we did come across this , twice in fact , both higher mileage engines , I think from memory we did chain , tensioner , pulleys and pump , the first one we looked at the possibility of just doing the minimum as the customer asked us to do for cost reasons , but once we had compared all items it was decided that the only way to do it was to replace all .

The problem we believe started with the normal chain stretch , that in normal circumstances would be catered for with the tensioner , but then once these got to maximum adjustment it started to damage the sprockets and eventually jumped a tooth .

Both these cars we did were not used as they were intended by ford , the sci was designed for motorway use where they could return very good fuel consumption at constant cruising speed , both were ex lease cars that had been sold into private hands and used just around town , probably sold with the idea that they would return good consumption figures even though around town they were terrible to drive , little power and not very flexible . This we believed contributed to the problems .

Hope this helps .