S Max Ecoboost - engine light on / rough idle. Ideas?

[Russ_H]

I've been offered a 2011 S Max 2.0 Ecoboost for a good price but it's not running right.
Engine light is on - runs OK at speed but rough at idle.

I know these engines have had issues with carbon build up and some failures in Focus STs.
Before I get too involved does anyone have an idea what the issue could be?

The car in general is in great condition, FSH, good spec - however sold as seen, no warranty etc.

If it's relatively simple fix for £1-2k the deal makes sense otherwise I'll pass.

Any ideas?
Thanks