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  1. #1
    Senior Member Three Rings R3V3NANT's Avatar
    Join Date
    Apr 17 2010
    AZ Member #
    57767
    My Garage
    B6 A4 1.8TQ, B5.5 Passat 4M Variant,
    Location
    Dayton, OH

    Fixing misfire - checklist

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    First, the good news.

    They finally wrote it, and I finally got it:



    And the bad:

    I've had a 0420 code on my car for some time now. It's got nearly 130k on the clock, so a new cat isn't out of the ordinary, I suppose. I don't know anything about this car's history prior to about 100k.

    I've started getting misfires in cylinder 3 for some time now. I went through 3 coilpacks, each of which repaired it for about a week to 2 weeks, but this last time, it brought friends. I've got misfires in 1,3 and 4, and the 0300 code (random misfire.) I've switched the packs around and put in brand new NGKs, but I still have the same misfires. The old plugs were dirty, but not fouled with oil. There is some slight oil residue in #3 where the head and the valve cover meet. Unplugging the MAF did nothing to help.

    I know the fuel filter needs replaced; it's making a humming noise, mostly when it's colder out, and the Chilton's lists a clogged fuel filter as one of the first causes of misfire.

    Anyway, I ordered an 034 HFC, a new fuel filter, as well as a valve cover gasket set, and the new Hitachi coil packs. Is there anything else I should check or replace while I'm doing all of this? All of my coil wires look good and nothing looks to be leaking vacuum-wise.

    Model is in my sig. Thanks in advance.

  2. #2
    Senior Member Two Rings SLeal's Avatar
    Join Date
    May 27 2010
    AZ Member #
    59586
    Location
    Vancouver

    I too would love some insight as it seems I have a similar problem

  3. #3
    Veteran Member Four Rings Audi Skate Snow's Avatar
    Join Date
    Mar 31 2004
    AZ Member #
    1504
    My Garage
    C300 Sport and tools
    Location
    CA

    IF you have tried plugs and coilpacks then next would be injectors. Try swapping them around. Clear codes first and swap the cyl that is throwing the CEL to a cyl that is not throwing and see if it moves.
    BetaAlphaTau member #1.5
    R.I.P B6 A4!!!!!! 12/03/2005 12.63@108... stock 1.8 motor W/ GTRS.
    B6 A4 Avant, 2.0 Liter, 3071, Maestro

  4. #4
    Established Member Two Rings Xmenpl's Avatar
    Join Date
    Nov 25 2009
    AZ Member #
    51221
    Location
    Long Island

    Once my first coilpack failed, replacing it opened another can of worms...
    As soon as i touched the harness, due to age and heat wiring cracked on cylinder 2 causing misfires, random to say least.

    http://www.audizine.com/forum/showth...k-harness-grrr!

    Pop the rubber boot and inspect individual wires.

  5. #5
    Veteran Member Three Rings Trev's Avatar
    Join Date
    Nov 25 2007
    AZ Member #
    22840
    My Garage
    b6 a4tq, 95 Eagle Talon (Rip)
    Location
    British Columbia, Canada

    Whaaa???? They have hard copy manuals now? Bye bye you stupid Bentley repair manual that wont work on my laptop!!!!

    Hanes also has one now too! Which one to get?
    Some Go, No show
    02 Qtip, Apr II+ 93Oct, tt-225 injectors, Ecode fmic, W/M Injection, Magnaflow 16601,TT225 Down Pipe, VMR test pipe, APR TIP, Forge 007, Vag-Com, Podi V2, RS4 LSB, ECS Snub, USP front lower, S4 Front Brakes, Slotted/Dimpled Rotors f/r, SS Lines f/r, 19x8.5 & 19x9.5 RPM 505's, RNS-E

    Wish List
    Custom fab intake heat shield, Custom fab system in trunk, Adjustable Coilovers, S4 blades, DTH side skirts

  6. #6
    Senior Member Two Rings SLeal's Avatar
    Join Date
    May 27 2010
    AZ Member #
    59586
    Location
    Vancouver


  7. #7
    Senior Member Three Rings R3V3NANT's Avatar
    Join Date
    Apr 17 2010
    AZ Member #
    57767
    My Garage
    B6 A4 1.8TQ, B5.5 Passat 4M Variant,
    Location
    Dayton, OH

    Quote Originally Posted by Trev View Post
    Whaaa???? They have hard copy manuals now? Bye bye you stupid Bentley repair manual that wont work on my laptop!!!!

    Hanes also has one now too! Which one to get?
    I preordered it on Amazon right after Christmas (I don't remember how I even came across it) and got it in the mail yesterday. The Bentley manual hates my computer, and my computer hates it, so paperback's the way for me now.

    EDIT: I think the Chilton's a little more detailed than the Haynes, but I can't remember if it's the other way around or not. Either way, you really can't go wrong for the price.
    Last edited by R3V3NANT; 01-26-2011 at 06:13 PM.

  8. #8
    Senior Member Three Rings R3V3NANT's Avatar
    Join Date
    Apr 17 2010
    AZ Member #
    57767
    My Garage
    B6 A4 1.8TQ, B5.5 Passat 4M Variant,
    Location
    Dayton, OH

    I switched injectors #1 and #2, seeing as only #2 didn't throw a misfire. All the injectors looked dirty, but not horrible.

    I also bought a can of fuel injector cleaner (similar to the Seafoam but I don't remember the brand) and put that in, and then reinstalled everything. OBD read just one misfire, in #1, so I switched it for an old coilpack I had lying around, and now it runs fine.

    Hopefully everything will hold till the Hitachis arrive.

  9. #9
    Senior Member Three Rings
    Join Date
    Dec 31 2010
    AZ Member #
    68881
    Location
    Chicago land

    Cat failure is often due to misfires or oil consumption. Also looking at an injector doesn't tell you much. the dirt is on the inside of the injector where you can.t see it, not the tip. also injectors often fail electronically. IE a shorted winding inside of the injector.

  10. #10
    Senior Member Three Rings
    Join Date
    Dec 31 2010
    AZ Member #
    68881
    Location
    Chicago land

    make sure you fix the misfire before putting on HFC or you'll risk damaging the new one.

  11. #11
    Senior Member Three Rings R3V3NANT's Avatar
    Join Date
    Apr 17 2010
    AZ Member #
    57767
    My Garage
    B6 A4 1.8TQ, B5.5 Passat 4M Variant,
    Location
    Dayton, OH

    I had the 0420 code prior to the misfires; I was becoming under the impression that it was causing the misfires, not the other way around.

    I'll make completely sure everything is cool before the HFC goes on. I really wouldn't want to ruin it.

  12. #12
    Senior Member Three Rings
    Join Date
    Dec 31 2010
    AZ Member #
    68881
    Location
    Chicago land

    P0420 is a cat efficiency code meaning the the cat is no longer doing its job. It wouldn't not cause a misfires nor any other driveabilty problems.

  13. #13
    Senior Member Three Rings
    Join Date
    Dec 31 2010
    AZ Member #
    68881
    Location
    Chicago land

    Usually high flow cats will also throw a P0420 unless you have a chip to delete that part of your emissions or you use an O2 spacer. not sure if you have any emission testing in Ohio or not?

  14. #14
    Established Member Two Rings
    Join Date
    Feb 05 2011
    AZ Member #
    70506
    Location
    Pa

    ICM (ignition control module) located on the top of the air box usually throws misfire on cylinder 2 only.



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