po305 code most common cause?

Question

the code just came on ,new plugs a week ago.i changed the coil pack eraced the code but it came back on.

Answer 1

P0305 Misfire number 5 cylinder

The number 5 cylinder on a Ford is unique, If there was a slight leak at the fuel pressure regulator its the number 5 cylinder that will set a misfire condition, The EGR can also set a misfire when it does not properly close and it the number 5 cylinder that misfires.