Hello everyone,
Long time lurker...finally decided to post. I'm at my wits end with our 2012 Mazda 3 Hatchback GS Sky. Car has 124000Km on it and P0303 showed up about 2 months ago, figured it was the plugs so I purchase a set of NGK-ILKAR7L11 to replace the factory plugs. Plug from cylinder 3 had alot of carbon on it. Replaced them all, erased the code car was fine for a few days then the code came back. Searched online about the misfire codes and found a Mazda TSB that talked about updating the ECM to the latest version to address the problem. Brought the car to the Sudbury, Ontario Mazda dealership with the TSB and the plug i replaced from cylinder 3....service guy didn't seem to enthused about what I brought him and wasn't convinced that was the problem. Couple hours later I get a call from the dealership telling me they would need to removed the cylinder head and decarbonize it, all for $600. I said "uh I don't think so", went to canadian tire bought a can Seafoam with the red plastic straw and ran one can through the intake, then went for a spirited drive..without the wife of course!....Code didn't go away. So read some more posts online and decided to take the intake manifold off and went ahead sprayed them with seafoam then sand blasted all the intake valves with crushed walnuts. The valves came out nice and clean. Put everything back together cleared the code and it ran pretty good for about a week, then P0303 came back. So I started thinking maybe I have a bad coil pack, so I swapped the coil pack from Cylinder 3 with Cylinder 1, removed cylinder 3's spark plug and cleaned it with brake cleaner cuz it was starting to have crud on it. Cleared the code and a couple days later I got P0303 code again. I was hoping I'd get a P0301 then I would know it was a bad coil....but no luck.
So that's where I am now....what the hell do I check next???
Do I take the cylinder head off and clean the crap out of it??
Dirty fuel injector??
Thinking of taking the EGR off and cleaning that, but not sure if that will make a difference.
Sorry for the long post, but I'm about to put a pick axe through the hood.