The dreaded P0303 - new purchase & unknown mods :(
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This is a discussion on The dreaded P0303 - new purchase & unknown mods :( within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; The dreaded P0303 - new purchase & unknown mods Hi guys, Just bought an 07' WRX. 54k Miles - front ...

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    The dreaded P0303 - new purchase & unknown mods :(

    The dreaded P0303 - new purchase & unknown mods

    Hi guys,

    Just bought an 07' WRX. 54k Miles - front end accident history. Unfortunately the previous owner didn't know much about the car. I can see a short ram intake of some kind and some sort of intercooler kit (has Mishimoto hoses). If you see anything else besides that and the grounding kit - let me know. This could be caused by unknown injector sizes or other unknown mods. The only symptom I have is some overall hesitation throughout the whole power band, doesn't feel as strong as it should, but then again I have only once driven a stock 07 from the dealers lot.

    Click image for larger version. 

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    Since I bought it...

    Has a new complete OEM pump assembly (had low fuel pressure), new MAF (last one mysteriously read %20 compensations causing the engine to run rich (dealer told me when they fixed it)). If you want more details on that fix check out my first post:
    New '07 WRX Owner

    The dealer also told me plugs were replaced about 20 000 miles ago, and the ECU has been flashed of any possible tunes that may have existed.

    I read through this:

    IF YOU HAVE A MISFIRE CODE ,PLEASE READ THIS!!!

    Before I start trying all of these things and spending buckets of cash...I was wondering if you guys have any ideas or suggestions as to what the issue is? I will use this post to log this issue fix to help others in the future. If you think this is lack of ECU tuning issue or unknown engine mod issue, let me know, otherwise I will troubleshoot the car as per OEM spec.

    Next thing I'm gonna try is cleaning the injectors with Seafoam first, then Lucas upper cylinder cleaner with some long highway drives.

    Check engine light + flashing cruise control light

    P0303
    Fuel sys 1: CL
    Fuel sys 2: CL - fault
    Calc load(%): 16.47
    ECT(f): 199
    STFT B1(%): -10.94
    LTFT B1(%):
    -3.91
    MAP(inHG): 8.27
    Eng PRM: 2794
    Veh Speed(mph):
    13
    Spark Adv(degrees):
    51.00
    IAT(F): 149
    MAF(lb/min): 1.50
    TPS(%): 16.86
    Air Status: UPS
    O2S B1 S2(V): 0.00
    O2S B1 S2(V): 0.00
    OBDSup: OBD2

    Let me know your thoughts on what the next step should be.

    Cheers,
    Richard

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  3. #2
    Moderator Donkey's Avatar
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    Start with the easiest/cheapest on the list and worth to the hardest/most expensive. The whole purpose of making that list is to give you ideas on where to start looking.I would pull the plugs and check to make sure the gap and part number are correct. At the same time check the coil pack connectors and towers. I generally stick a little dielectric grease on the harness plug and tip of the sparkplug tower on the coil pack.
    Resident Adviser @ WTF Tuning, LLC
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    Registered User Obeisance's Avatar
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    What is up with that IAT?!? Isn't the intake air temp measured at the MAF? (mine always reads a temperature near ambient)

    Also, do you have any way of logging the A/F ratio?
    David - '05 WRX

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    Considering the work i've already done, and eliminating the worst case scenario stuff I think it could be one of the following:

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

    8. Excessive PCV blow by. PVC gases will effectively lower the octane content of gasoline/petrol. (no idea how to diagnose if this is an issue though.)

    11. Bad/loose coil pack or coil pack connector. Test coil pack and move to other cylinder to see if DTC changes. Also check the tower boot for corrosion.

    Bartender last night told me that since cylinder 3 is close to the turbo, so wires and coil packs and stuff can go first due to heat. Any truth to that? That was what the issue was with his '02 apparently same exact issue. Anyways, ended up giving the guy a good tip

    Also, the code seems to throw right after a very warm start, but I think I can feel the hesitation all the time, even when it doesn't throw a code.

    Lastly, A/C compressor seems to make a squeek when it kicks in. I'm going to change the accessory belt asap to see if that goes away.

    Will let you guys know how it goes. Let me know if you think of anything else.

    Cheers.

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    and the Funky Bunch Calvinball's Avatar
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    First thing I would be doing with that car is not driving it until I could address engine management. You've got the intake, which would want that anyways, but I think I also see a missing stock heat shield, which would indicate an aftermarket downpipe, which would also require a tune.

    Without knowing anything about the car's history, I would personally assume it was incorrectly modded (meaning slapped on parts and didn't address the tune for them) and play it safe. There may be mechanical issues going on as well, but if the engine management isn't there, then they'll just come back.
    - Will
    First Mods: What to do and what not to do
    Current Car: 2014 Golf TDI
    Previous Cars:2012 WRB WRX Hatch, 2004 RSX-S, 1998 Grand Prix GTP
    "Isn't it amazing how smart you feel when you just aren't being stupid?"

  7. #6
    Moderator Donkey's Avatar
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    The #3 is closest to the turbo,but if you look where the turbo is located vs the coil pack I don't see how it is going to get anymore heat than the others.
    Resident Adviser @ WTF Tuning, LLC
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    Calvin, you're right. I'm going to try to find a safe base tune online this weekend and see if I can partially address the lack of tune for now. If you have any suggestions in that regard, I am going open source. Early next week I'm going to get all the coil packs and stuff checked by a good electrical guy that I trust.

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    If anyone has any ideas on a base tune I can do with Rom Raider, or something like that, let me know. I'm going to be saving a ROM copy of my ECU right away here with the cable I just got.

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    I was having simular issue, in fact for a second i thought that was my under hood, looks very simular. I'd recommend checking the ECU to see if there is anything pluged into it, in-line to/from it ETC. just found out sunday that i had a piggyback computer on my ECU causing me a **** ton of grief!

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    Hey guys. Just flashed my ECU with what seems like a safe stage 1 map.

    RomRaider • View topic - 06-07 USDM WRX MT: Stage 1 (A8DH201X/A8DK100X)

    It runs much smoother. I feel like I should be doing more adjustments for my short ram intake though. Can anyone help with this? I think I might post my log for others to review in the appropriate section of the forum.

    No new misfire codes thrown yet in the last few days, but I just flashed my ECU tonight - I will reply if anything else shows up or if I find another issue. Otherwise, if you are reading this thread from the dead, please assume that it was a tune issue.

    Cheers,
    Richard

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    Cylinder 1 Misfire - tried almost everything!

    Hi,

    I've tried almost everything to solve my Cylinder 1 Misfire (P0301), but nothing is fixing it.
    I have a 2006 WRX with 160,000 KM.

    I've read the IF YOU HAVE A MISFIRE CODE ,PLEASE READ THIS!!!
    1. Have replace spark plugs - NGK Iridium ALFR6B
    2. removed and cleaned injectors in machine. Installed new Subaru fuel filter. only run 91 or 93 octane.
    3. Compression test passed
    4. Cleaned and swapped in new MAF sensor
    5. Checked for Vacuum leaks
    6. Cleaned battery ground, will clean intake manifold
    7. New timing belt installed (regular maintenance interval)
    8. checked PCV
    9. Originally used Lucas upper cylinder cleaner, and put 93 octane in.
    10.
    11. Coil packs have been swapped and code didn't follow swapped coil.

    New battery installed.
    Installed new Knock sensor
    Installed a K&N air filter.
    Everything is stock otherwise.

    There is a definite hesitation from the car, the Turbo also does not kick in anymore (not sure if this is a fail safe).

    I've been working with my local mechanic to try and solve it as well taken to a Subaru specialist in Vancouver, B.C.
    Compression check. Spec is 142 - 171 psi. Maximum difference is 7 psi. #1 = 124 psi, #2 = 125 psi, #3 = 120 psi, #4 = 125 psi. Running compression test: #1 = 90 psi, #3 = 90 psi. Cylinder leakage test - ok. Cylinder smoke test - ok. Intake system smoke check - ok.

    Remaining to try:

    ECU flash
    Valve clearness check (even though compression is fine?)
    Exhaust value inspection (even though compression is fine?)
    Head gasket inspection (even though compression is fine?)
    Flywheel

    Recommendations on which to do first?

    Huge thanks!
    James

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