If I was away from the airfield, and my engine began to sound unhappy, the FIRST THING I would do is select a nearby field, land on it, and then call for help if needed....This order of priorities I have been told is quite wrong.
Why? Yes, pick a field, but if it is still running, get/keep what height you can and fly field to field to the nearest airfield, depending of course on how bad it sounds and if it gets worse as you are going.