DutaTorq stalling problem

[the daddy]

Evening all,

I have use of a Fiesta in Spain and it’s a 1400 Duratorq engine. Great little car, but it stalls intermittently on low revs. Whilst I have checked out the forum for other questions like this I need a bit of help in sorting it - the weather in Spain is great, but the mechanics don't seem to be as pleasant! It’s been to Ford who claim to have checked for fault codes and have found none.

I see form another thread that the TDCi engine can stall if the engine dips below 750rpm and this seems like it could be the same fault. With the aircon on and I pull up at a junction it will stall 50% of the time, with the aircon off its more like 10%.
SO my questions are - Can I adjust the tickover revs of the car, or is it all computer based stuff?
and - Do you think the TDCi and duratorq engine work (or stall) in a similar way?

Help!!!