P0301 Ford -

Question

why at random an 09 mercury mariner 3.0 engine during hard accerlation throws the po301 engine code at 30k miles

Answer 1

Hi there,

This would commonly be caused by a faulty ignition coil on cylinder #1. When you are under hard acceleration it's putting the coil in it's failed condition. I would swap it with one of the cylinders next to it and see if the misfire moves with it. If it does, then you know the coil is faulty.