OBDII errors P0302,0303,0304
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This is a discussion on OBDII errors P0302,0303,0304 within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; Hi Peeps, Ive been searching around and cant seem to find a reason for my car throwing the following errors ...

  1. #1
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    OBDII errors P0302,0303,0304

    Hi Peeps,

    Ive been searching around and cant seem to find a reason for my car throwing the following errors -

    P0302,0303 and 0304 - All missfiring cylinders. The car runs ok, seems to have the odd off day but keeps throwing those errors. I have changed the plugs / serviced (only thing not changed was the fuel filter), changed all the coilpacks, reset the ecu, running on 99RON petrol but still the same.

    Im getting circa 280 miles to a full tank.

    Im kinda stumped! cam sensor? fueling? Its not throwing any errors for that, Ive run new earth cables to the block, head and chassis.

    This is on a 2003 Bugeye WRX, only mod is a decat downpipe and thats about it for engine mods.

    Hope someone can help

    Cheers

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  3. #2
    Registered User oguitar's Avatar
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    Make sure the coilpacks are properly installed. Some people have issues with the little tab breaking and they need to tie wrap them. Also try changing out the fuel filter. That is an easy job.
    Life is like riding a bicycle in order to keep your balance you must keep moving.

  4. #3
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    Quote Originally Posted by oguitar View Post
    Make sure the coilpacks are properly installed. Some people have issues with the little tab breaking and they need to tie wrap them. Also try changing out the fuel filter. That is an easy job.
    Hmm... Well it was throwing the errors before changing the coilpacks and still throwing them after so hopefully those should be ok! ill double double check them though. Ill check which plugs I have in there too as I cant rememeber off the top of my head. Ill change the fuel filter and see what happens.

    It does flash the engine light every so often but it goes back off straight away and no errors logged...

    I have a scanguage II fitted so can read the errors straight away and clear if necc. I can run a few graphs of timing etc from an obdII if anyone has the time to have a look and poss point me to the problem?

    Thanks for reply

    John

  5. #4
    Moderator Donkey's Avatar
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    Most likely senarios are:

    1. Wrong, worn or incorrect gapped spark plugs. You should run only NGK stock range plugs gapped to 028.

    2. Clogged injectors. Have the injectors cleaned or at least run several bottles of a good injector cleaner through the engine.

    3. Carbon build up on motor. Real common on EJ205's. Get some BG Chemtool, GM top end cleaner or other type of carbon remover. GM top end cleaner seems to work really well.

    4. Oil or dirt build up on MAF sensor. This causes an incorrect load reading which make for AFR corrections out of line. Misfires can result. Remove the sensor, place in plastic bag. Spray out with CRC MAF cleaner or NON clorinated brake cleaner.

    5. Vacuum leak. Check the turbo inlet pipe where it connects to the turbo. This pipe is famous for ripping and causing a huge preturbo leak.

    6. CLean the ground cables that run to the intake manifold. These are sensor grounds and must be kept clean.

    7. Cam timing. Check and make sure the timing belt has not jumped a tooth or two.

    8. Excessive PCV blow by. PVC gases will effectively lower the octane content of gasoline/petrol.

    9. Check valve clearances.
    Resident Adviser @ WTF Tuning, LLC
    2002 FORESTER S
    1998 FORESTER S




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