Had erratic rpm on our car,so I took it to the main stealership ,sorry dealership who new bugger all about this model.they could not sort it.£815 poorer .Right ,what I did was loosen the pozidrive screws on the throttle body sensor( small round black thing with a multi socket on it)on the intake body , and once you have undone the screws move the sensor by about 1 mm.and retighten the screws.start the engine for a millisecond then turn it off.
repeat this ten times. This re educates the cold start settings. you should then have a fast idle setting around 1800rpm.
If you have an even fast idle then as the engine warms it should automatically set the hot running speed.
hope it works for you as it cured ours.
P.s. Main dealerships appear to employ technicians and not proper mechanics.I have the bills to prove it.Good luck
Also try Cataclean in your fuel it is brilliant :
