Ford Repair: engine misfiring ang backfires, egr valve, engine compartment

Question
i have a 1998 expedition with 188,000 miles on it. it misfires and backfires under accelleration. engine light comes on. then it will blink. then stay on. the codes it is giving are p401, p301,p307,p306

Answer
Your first code is the key I believe. It is probably causing the other 3 codes, which are misfires in the numbers 1,6, and 7 cylinders. The code is for insufficient flow to the EGR valve. Have you recently cleaned the engine compartment? What were you doing when this started, was it raining?