Misfire CEL problems! Please help.
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This is a discussion on Misfire CEL problems! Please help. within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; So I recently bought a stock 2002 WRX with 145k, this is my first subie and I'm really new to ...

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    Misfire CEL problems! Please help.

    So I recently bought a stock 2002 WRX with 145k, this is my first subie and I'm really new to working with cars. It's giving me a bunch of different misfire codes ranging from P302 to P302-3 and even P302-3-4 or P301-2-3. The idle seems fine, it stumbles a very small amount every now and then but nothing I would consider out of the ordinary. I am getting inconsistent boost at higher RPM ranges though. It's like the boost will surge then die down then surge then die down again but in rapid succession. The CEL that comes on doesn't blink and going into high RPM ranges doesn't trigger it. I've done a few things to try to fix the issue already which I will post below. I'm completely stumped on this and I would seriously appreciate some help. Thanks in advance guys.

    Replaced spark plugs - NGK Iridium
    Swapped coil packs
    Cleaned fuel injectors
    Cleaned MAF
    Replaced fuel filter
    Replaced crankshaft position sensor

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    Registered User pete25r's Avatar
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    I would do a compression test if I were you. I you replaced all the plugs and coil packs, cleaned/replaced fuel parts, then that doesn't leave much else.

    I haven't troubleshot random-ish multiple misfires before but a compression test couldn't hurt.
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    Thank you both for replying to my issue, and Donkey I was kinda waiting for you to respond. I have been looking at that thread for the past week trying to figure out my problem but I still can't fix it. Out of everything that I have tried what would be the next logical step? My problem is that these misfires are keeping me from getting a New York state inspection which is keeping me from registering my vehicle. I'm on temp tag #2 now and after this one is up I can't get another one so I really need to figure out what is going on. Also I have tested the vacuum lines by spraying flammable brake cleaner over the lines and listening for an RPM change at idle. I didn't hear anything but I feel like I didn't check it as thoroughly as I should have.

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    Registered User cogito's Avatar
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    Quote Originally Posted by pete25r View Post
    I would do a compression test if I were you. I you replaced all the plugs and coil packs, cleaned/replaced fuel parts, then that doesn't leave much else.

    I haven't troubleshot random-ish multiple misfires before but a compression test couldn't hurt.
    ^ +1
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    Quote Originally Posted by pete25r View Post
    I would do a compression test if I were you. I you replaced all the plugs and coil packs, cleaned/replaced fuel parts, then that doesn't leave much else.

    I haven't troubleshot random-ish multiple misfires before but a compression test couldn't hurt.
    How do I do a compression test?

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    Registered User cogito's Avatar
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    You could also have a bad ECU.
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    Quote Originally Posted by cogito View Post
    You could also have a bad ECU.
    I have also thought about that because the person who I bought it from told me the ECU needed to be reflashed, but I took it to the dealer and they said I have the most up to date software on it and there is nothing they could do. Is that something I could fix with ROMRaider instead of buying a whole new ECU?

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    Moderator Donkey's Avatar
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    Quote Originally Posted by Equipmunk View Post
    Thank you both for replying to my issue, and Donkey I was kinda waiting for you to respond. I have been looking at that thread for the past week trying to figure out my problem but I still can't fix it. Out of everything that I have tried what would be the next logical step? My problem is that these misfires are keeping me from getting a New York state inspection which is keeping me from registering my vehicle. I'm on temp tag #2 now and after this one is up I can't get another one so I really need to figure out what is going on. Also I have tested the vacuum lines by spraying flammable brake cleaner over the lines and listening for an RPM change at idle. I didn't hear anything but I feel like I didn't check it as thoroughly as I should have.
    What mods are on the car?
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    Quote Originally Posted by Donkey View Post
    What mods are on the car?
    None to my knowledge. The seller told me the car was stock and I don't see any indications to make me think otherwise.

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    Bump. Please help, still having this issue.

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    Registered User Obeisance's Avatar
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    I am interested to know if datalogging could help pinpoint the issue. How is a misfire event confirmed? Is it just seen by the ECU as an excess of unburnt hydrocarbons in the A/F sensor in the headers?
    David - '05 WRX

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    I've only used an OBDII reader to check. I don't currently have a OBDII to USB to log my information and I don't even know what software to use. Could this be masked by the tactrix cable and ROM Raider? Even if it doesn't solve the issue I just absolutely need to pass my NY state insp so I can register my vehicle.

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    Moderator Donkey's Avatar
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    Try cleaning the all the factory grounds and ground points in the engine bay. Or even add a cheap grounding kit and see if that helps. Also pull the cam position sensor and wipe off the face of it.
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    Quote Originally Posted by Donkey View Post
    Try cleaning the all the factory grounds and ground points in the engine bay. Or even add a cheap grounding kit and see if that helps. Also pull the cam position sensor and wipe off the face of it.
    Okay I'll do that, thanks. As far as the compression test, what kind of numbers should I get and what do I do if it fails? Also, if I still can't figure out what's going on will the tactrix cable with RomRaider at least mask my issue so I can pass my emissions?

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