How do you fix a P0303 cylinder 3 misfire on a Ford Focus 2002?

Answer 1

I had the same problem. The misfire code can be for a number or reasons. One oddity of the focus DOHC engine is the placement of the plugs, relative to the top pan. THey are deep inside the engine. The plug wires have a boot on top of them to prevent moisture from getting down in it. This does not always work. Before doing any crazy diagnostics, pull the #3 wire up (when facing the car, the #3 plug/cyllinder is the 2nd from the right - left to right, 1,2,3,4) from the toppan to inspect the plug. If you see water in there or any corrosion, it is most likely the plugs. If not, it is possible you may have a bad wire to the #3 plug. If there are some miles on the car, new plugs and wires are always a good bet anyway, just make sure you don't pull the plugs out with water / particles near the base of the plug - you don't want a lot of junk falling in there. There are other possiilities like the PCV or injector, but the simplest solutions are usually the right one.