Trying to figure this out!!!

Discussion in 'Modifications & DIY how-to' started by Al.SpecB, May 29, 2012.

  1. Al.SpecB

    Al.SpecB Member

    Wats going on guys? Here is my problem. I got a 07 legacy specB. Back in December I had a misfire on cylinder 3, This is what i did:

    1)I put new ngk plugs and a new oem coil on cylinder 3
    2)I pulled the injector and inspected it and all was good.

    Then some how upon putting everything back together the misfire went away.

    Still concerned I took it to all pro and had the compression checked on the cylinder and it passed.

    So everything was good up until two or three weeks ago and the misfire came back on Cylinder 3. This time pretty much started over once again.

    1)I swapped coil around and no change still misfiring on 3.
    2)I put subaru OEM plugs no change.
    3)I swapped injector around and still misfiring on 3.
    4)I check the signals from the ECU to the injector and all was good.
    5)I was curious and I pulled the fuel pump and peeked inside the tank to make sure no trash was in the tank and there wasnt.

    After putting the fuel pump back together I started it up and NO Misifre.

    Im just going to mention this to see if anyone can maybe link it up. I had a P0171 System LEAN code. I didnt give it much thought I thought it was because of my MAF being dirty because I was over due for an airfilter so i put a new filter and cleaned the MAF, cleared the code a never gave it any thought.I also sprayed the engine down with carb cleaner to check for VAC leaks and I wasnt able to find any leak. With a ODB2 scanner I checked the reading of all the sensors and everything was fine for the lean code concern. The only thing wasn't able to check on the lean code diag was fuel pressure.

    So right now the car is running without issue. The thought and curioisty of what is causing this strange misfire is always lingering in my head. So Im asking you guys to give me some ideas on things to check or any advice so if and/or when it comes back Ill hopefully be able to pin point this misfire. Thanks for the help guys hopfully once summer classes get started agian ill be able to make time to go to the Tuesday meets.
     
    Last edited: May 29, 2012
  2. b reel

    b reel Active Member

    do you have any way to data log it? check fuel pressure?
     
  3. h23bb2

    h23bb2 Member

    I've noticed alot of these cars tend to throw misfire codes randomly. SOmetimes its real, sometimes its a ghost code.
    Can you swap out the cam position sensor with a known good one?
     
  4. Al.SpecB

    Al.SpecB Member

    B reel. I have some data logging in the scan tool I was using. But not enough to check all the sensors I want too like the cam position or crank position, injector pulse and everything eles. I'm working on getting the right disconnect tool to remove the fuel line and get the right line connectors for the fuel pressure gauge.

    H23BB2. I wouldn't say mine problem is a ghost problem because I feel a steady hard misfire even when accelerating an it jerks hard. I'll have to track down a good cam sensor a swap it out and see what it does but the problem is gone now so I'll have to wait till it comes back to test it out. Thats probably the most troubling part of it that it can go away for weeks or months and then come back.
     
  5. sikwrx04

    sikwrx04 Member

    Got the same problem with my car, misfire in cylinder 1 and 2 gonna try to put new spark plugs in and see what happens....
     
  6. h23bb2

    h23bb2 Member


    a hard jerk during acceleration sounds like knock and the ecu pulling timing or a leaning out of the afr..
     
  7. Berzerklo

    Berzerklo Active Member

    OP - is your car stock?
     
  8. Al.SpecB

    Al.SpecB Member

    Yea the car is all stock. I driven it hard a couple times since it last came on and the light has not come on. I got somethings in the works to check fuel pressure and the regulator in the next couple weeks. Ill let you guys know how that goes.
     
  9. ChrisW

    ChrisW Member

    probably a short in the wire going to the coil, would make sense since youve ruled out the injector and the coil by swapping them around.
     
  10. b reel

    b reel Active Member

    could be just a bad ground, check the two on the top of intake manifold and the obvious negative on the battery. Pull them and clean the contact areas then make sure you have them nice and tight.
     
  11. CelticPride

    CelticPride Banned

    Subaru grounds are notorious. One of the first mods I recommend is a grounding kit for any Subaru esp Turbo ones. Mine did that in stock form. Added grounding kit and that fixed it.
     
  12. h23bb2

    h23bb2 Member

    seen the car yesterday and datalogged it. He's currently not having the issue and all seemed well with the datalogs so we'll see if it comes back (i suspect it will).
     
  13. Al.SpecB

    Al.SpecB Member

    Alright here is an update. Earlier this evening I went out the my girl to go eat and I was going down 85. I was just cruising at highway speed when all of a sudden I felt the jerking of the misfire but it wasn't consistent very intermittent. So I settled down the rpms and I get back on it pretty good and I could deffinettly feel the stumble and had some what of a lack of power. So I'll see what comes of it during the week and if I am able to find when exactly it causes it ill do some further diag and maybe see if allpro can help. I'm still now sure what can be causing this. But I'll deffinetly let you guys know.
     

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