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Help PO303 & 304 cylinder misfires

09 Subaru Outback 4 cylinder. I replaced the spark plugs and cords and the codes went away for about a week. I have a friend who thinks its my fuel injectors but it could also be my coil. How do I tell what it is?

Swap those components to a cylinder without a miss, and see if the miss moves to those cylinders.


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Swap the coils first. Then see if the misfire moves. If they don’t, then repeat with injectors.

Can that still be done with a coil pack?

Thought you had coil on plug. Sorry. But you can swap wires to check them.

What kind of wires are they? I have bought new wires at autozone and they turned out to be pure junk. Lasted about a week and I had to put the old ones back on. Now I dont skimp on them.

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