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Thread: P0303 Misfire Done a bunch of stuff

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    Default Re: P0303 Misfire Done a bunch of stuff

    Glad to hear things r looking better.. my wifeís 2012 Mazda 3 skyactiv is throw a misfire code as well.. I should start with the injector first & work my way down I suppose.. I already swapped coils, might get her to take the car into the dealership to remove the carbon buildup as she hasnít had it done yet..

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    Default Re: P0303 Misfire Done a bunch of stuff

    Quote Originally Posted by chienlaid View Post
    Another update on this problem. After running great for a few months P0303 started coming back on and off, especially on cold days. Bought a compression tester, all 4 cylinders checked out properly. Ended up buying an injector from Rock Auto, replaced it and the problem is solved. Been running for over 6 months through cold winter weather with no issue.

    Hopefully this helps someone.
    Hey,
    I have same issue with my Mazda cx5, I am about to change Fuel injector of cylinder# 3, I'm Wondering after replacing Injector, do I need to do fuel injector coding?
    or just replace old injector with new one , that it.?

    Thanks

  3. #28
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    Default Re: P0303 Misfire Done a bunch of stuff

    Quote Originally Posted by aman1033 View Post
    Hey,
    I have same issue with my Mazda cx5, I am about to change Fuel injector of cylinder# 3, I'm Wondering after replacing Injector, do I need to do fuel injector coding?
    or just replace old injector with new one , that it.?

    Thanks
    I didn't do a damn thing. Replaced the old with new and that's it. Probably took the computer a bit to learn, but never noticed.

  4. #29
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    Default Re: P0303 Misfire Done a bunch of stuff

    Quote Originally Posted by chienlaid View Post
    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.
    is there any update on your situation?

  5. #30
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    Default Re: P0303 Misfire Done a bunch of stuff

    Quote Originally Posted by aman1033 View Post
    is there any update on your situation?
    Ended up pulling all the injectors and letting them soak in carb cleaner over night. Put them back in the car the next day. Walnut blasted the valves, just because, don't know if it really needed to be done. Installed new plugs NGK-ILKAR7L11, it's been well over 100K and haven't had a single misfire since. Car is now at 262K.

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