2.0 litre petrol engines are the cheapest and the most reliable motor available in the ford smax range. They are being driven by a timing chain as opposed to the timing belt and require very little maintenance in comparison to the other cars in the smax range. Not only you buy it cheaper, the annual cost on maintenance and road tax is much less than any of the diesel engines or the volvo 2.5T.
There are no common faults for this motor. Refer to general smax faults section for trim and other problems.
Said that, I had myself a problem of non stable idle revvs. At traffic lights the car was almost stalling. No problem with the throttle.
This is definitely not a common problem but if you encounter this the fix for mine was replacement of the idle valve after a year long investigation by two separate ford dealers.