[quote author=Cain link=topic=49413.msg3677251#msg3677251 date=1275149815]
PO300 - Multiple Cylinder Misfire or any misfire codes 301,302,303,304 should try this. I did it and it had a smoother cold start and completely fixed the po300. Stretch the coilpack springs until they poke out of the boot about a half or 3/4 of an inch, put dielectric grease on it, and carefully align it when you put it back on. It seems that the spring wires retracted slightly from changing the plugs and wasn't making a strong connection.
I joined this forum to research problems other Mazda3 owners are having... my 06 Mazda in back at the dealer for the 3rd time since the end of January for a repeated P0300 CEL. The plugs have been changed, but the light still persists. I would be inclined to think the sensor is faulty, but the engine is running too rough (not like it use to). The dealership cannot find the problem... like this is all in my head!! (Yes, I'm a girl) Cain, your suggestion will be relayed... has anyone done a leak down test for the valves? (recommendation by a former Nissan mech) Naturally, I have 4 payments left on this car, that I used to like a lot... at least I have an extended warranty, but that doesn't do much good if the dealer can't even figure out what is going on!!