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This is a discussion on IF YOU HAVE A MISFIRE CODE ,PLEASE READ THIS!!! within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; Originally Posted by JuSteve Just to reiterate. I've worked on lots of cars old and new and weird things happen. ...

  1. #31
    Registered User JTFrost's Avatar
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    Have 03 WRX - been dealing with P0303 & P0301 CEL

    Quote Originally Posted by JuSteve View Post
    Just to reiterate. I've worked on lots of cars old and new and weird things happen. Example:

    I have a 2004 wrx all stock except for the resonator box was removed. Sounds kinda nice

    I was driving and the CEL came on. Ran the code P0301 cylinder 1 misfire. I started with the plugs and all of them were fine. I replaced them anyway because it was cheap. Then I switched the coil packs from 1 to 3. Nothing changed. Still pulled the same code. Then I checked the wires. All were fine. Then I ran a fuel injector through 2 tanks of premium gas. Finally my buddy said to pull the MAF plug while it idles and see if it improves. Guess what...

    So I cleaned off the MAF and it runs fine. Just because it says P0301 doesn't necessarily mean that's the issue. That's just the first place the computer detected a problem so I had to go "further upstream."

    Sometimes I wonder why I even bother lifting up the hood but there's always something new to learn.

    Anyway, don't get tunnel vision like I did and if you submit something to the forum, give as much info as possible because it wasn't until I stopped thinking about the plugs (which were totally clean anyway) and considered that only the idle was rough. I never experienced a loss of power. Be thorough and provide details. Cheers

    I'm sure this is a noob question to ask but what is the MAF plug? I also have an after market flywheel with a K&N air filter, Cat Back HKS exhaust. Any help is appreciated since there are so many different approaches on this forum, Thanks!

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  3. #32
    He simply abides. SD_GR's Avatar
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    On the intake there is a small electric device with a harness clipped to it. Is is about the size of a match box and located on the top of the intake after the filter section, and is black. This is the mass airflow sensor. Periodically it can accumulate dirt (especially if the filtration is sub-par -- read: aftermarket) and generate a PO171 "lean mixture O2 sensor" code or more rarely in my experience a misfire.
    WRX Info Links, Courtesy TheJ
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  4. #33
    Registered User 06scoobyrex's Avatar
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    Quote Originally Posted by JTFrost View Post
    I'm sure this is a noob question to ask but what is the MAF plug? I also have an after market flywheel with a K&N air filter, Cat Back HKS exhaust. Any help is appreciated since there are so many different approaches on this forum, Thanks!
    MAF= mass airflow
    lightweight flywheels are notorious for causing misfire CEL codes especially in bugeyes... Also oiled air filters are bad for our already touchy MAF sensors...
    Hawk-Eye Alliance #801
    The Impreza "this was repaired/replaced at what mileage" database (Please Contribute)
    http://www.clubwrx.net/forums/showth...57#post2688257

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    Hi,

    New here. Just brought my first Subaru as im mainly a Rotary or nissan guy. Anyway I have just brought a 1999 jap import wrx wagon which has a misfire. I have changed fuel filter which has helped a wee bit but my main question is how do i access the fault codes? Do i need a diagnosis tool or something? Also how do i read the fault code?

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    I don't know how you would go about it on a '99 WRX. I have an access port which can read the codes. But more than likely your nearest Auto Zone will check your CEL codes for free.

  7. #36
    Moderator Donkey's Avatar
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    Yes you would need a OBDII diagnostic tool to retrive the code. Once you have the code all you have to do is Google it or you can check here:

    A Complete List of all SUBARU OBD2 error codes - i-Club
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    Shot cheers guys. I will go through the options above. If no love will take it somwehere to get code.

  9. #38
    Registered User JTFrost's Avatar
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    I have the 03 WRX, would you recommend the NKG Platinum Spark plugs? I need to replace mine and I think this could be the reason for my misfire codes.

  10. #39
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    Quote Originally Posted by JTFrost View Post
    I have the 03 WRX, would you recommend the NKG Platinum Spark plugs? I need to replace mine and I think this could be the reason for my misfire codes.
    This is what Subaru recommend. See the owner's manual for the spec.
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    Man is a brute.... If you're cruel to him, he respects and fears you. If you're kind to him, he plucks your eyes out. Alexis Zorbas
    I lied. I cheated. I bribed men to cover the crimes of other men. I am an accessory to murder. But the most damning thing of all... I think I can live with it. And if I had to do it all over again - I would. Benjamin Sisko
    DISCLAIMER: Opinions expressed are the author's alone and are inherently worthless.

  11. #40
    Registered User crisco's Avatar
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    Quote Originally Posted by Drift FD View Post
    Hi,

    New here. Just brought my first Subaru as im mainly a Rotary or nissan guy. Anyway I have just brought a 1999 jap import wrx wagon which has a misfire. I have changed fuel filter which has helped a wee bit but my main question is how do i access the fault codes? Do i need a diagnosis tool or something? Also how do i read the fault code?
    yeah if you have a real jdm 1999 wrx, you will need to get an OBD1 reader, not OBDII. but yeah autozone should be able to read it, if they still have OBD1s laying around for those pre-1996 (USDM) cars
    --- 1999 Impreza WRX STI JDM Version 5 Sedan ----

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    Nice post and thanks for sharing.

  13. #42
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    I had misfire codes popping up all the time for no reason.
    I changed the battery and it never happened again.

  14. #43
    Registered User Lionheart153's Avatar
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    is the MAF trick doable on the 2011 wrx model? Im getting a misfire code on all cylinders and I feel like when I idle the car feels like its shaking. I get the feeling the ECU or something might be mis-reading the air flow or something.

  15. #44
    He simply abides. SD_GR's Avatar
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    Your 2011 should be under warranty. If so this is not your problem, it's Subaru Canada's problem.
    WRX Info Links, Courtesy TheJ
    Man is a brute.... If you're cruel to him, he respects and fears you. If you're kind to him, he plucks your eyes out. Alexis Zorbas
    I lied. I cheated. I bribed men to cover the crimes of other men. I am an accessory to murder. But the most damning thing of all... I think I can live with it. And if I had to do it all over again - I would. Benjamin Sisko
    DISCLAIMER: Opinions expressed are the author's alone and are inherently worthless.

  16. #45
    Registered User Lionheart153's Avatar
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    you are correct sir, but my dealership is a pain because I didn't really buy the car from them. they also dont have a loaner car for me says there cars are all gone, but i'm ready to let someone have it so tomorrow hopefully I can get something

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