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Thread: Cylinder #6 Misfire, only at ~6krpm

  1. #1

    Cylinder #6 Misfire, only at ~6krpm

    Starting this thread with things that I've already replaced:
    Spark Plugs
    Coil Packs
    Fuel Filter and hoses
    VANOS seals
    DISA O-ring

    Seems to mostly happen in 3rd gear at around 6000 rpm. It's pretty repeatable and irritating as the DME cuts the cylinder out completely. I'm thinking it is a position sensor because of the exact place in the rpm range as well as the only cylinder that it happens to.

    Edit: Also happens at part throttle at ~6k in third. I believe it is load independent. I'll have to be "that guy" and rev it in idle at see what happens.

    Anyone have tips for an issue like this?

    Freeze frame data from INPA:
    Last edited by DeathTrap; 11-28-2018 at 05:44 AM.
    2003 Blue ZHP Sedan @ 195k
    Paint chips | Current MIL: P0420 | Airbag Light | Poorly Sprayed Black Style 135s |Ugly Alcantara Steering Wheel | Trunk Squeak | Faded Shadowline Trim
    This car is not a peach. It is a precision instrument, and will be used as such.

  2. #2
    Join Date
    May 2011
    Location
    Charleston SC
    Posts
    6,153
    Ryan (rkneeshaw) is having this same problem...he's a member here but here's his post on e46f
    https://forum.e46fanatics.com/showthread.php?t=1242691
    Dinan CAI &Throttle body, ESS Tuning TS2, Bimmerbrakes gen3 headers, UUC SSK & DSSR. Achilles oil pump, VAC oil pan baffle
    M3 Motor mounts, UUC Trans mounts, Modified clutch style LSD 3.15, TMS front subframe reinforcement, Koni Yellow sports,
    H&R sport springs,
    UUC sway bars, BMW Perf. Rotors, UUC SS brake lines, Hawk HPS pads, CSL replica wheels,
    Rotora strut bar, FXR HID conversion, M3 Mirror conversion, BSW stage 1 speakers

  3. #3
    Ahhh. Good to see someone much smarter than me already on the case. Seems like we have the same thought process, which is good.

    I posted in his thread, might shoot him a PM as well. Thanks!
    2003 Blue ZHP Sedan @ 195k
    Paint chips | Current MIL: P0420 | Airbag Light | Poorly Sprayed Black Style 135s |Ugly Alcantara Steering Wheel | Trunk Squeak | Faded Shadowline Trim
    This car is not a peach. It is a precision instrument, and will be used as such.

  4. #4
    Join Date
    May 2012
    Location
    Northern Michigan
    Posts
    481
    I dont know if I'd say "smarter", but we definitely seem to have the exact same issue, which makes me feel a little less crazy

    I just shot you a PM. I haven't changed out my crankshaft sensor yet due to weather (car is hibernating in its cozy garage while it snows), but that is next on my list of things to try. Its also down to one of the only possible remaining things I can imagine could be causing this.
    2003 BMW 330i ZHP
    ESS Twin Screw Stage 2 - Wavetrac - Headers - Borla - BMW Performance
    Turner Motorsports - Powerflex - Hawk Performance

    Build thread: http://www.zhpmafia.com/forums/showt...yan-s-2003-ZHP
    Wheelwell: 2003 BMW 3 Series
    Fuelly: 2003 BMW 330i

  5. #5
    Not 100% the same issue but when I accelerate hard, the car rocks/jerks (steering wheel has no vibration, new tires, alignment). This is all after I changed 6 coils/plugs. I had a SES light, which my indy shop says one of the cylinders said it was misfiring and if it happens again, he'll warranty it. Well, SES light came back. Do you guys think the jerking is due to misfiring? Only happens when I accelerate hard.

  6. #6
    Join Date
    May 2012
    Location
    Northern Michigan
    Posts
    481
    The crankshaft sensor didn't solve this issue for me. I also just replaced the headers and verified I have no exhaust leaks.

    So now the list of things I've tried looks like this:

    • Swapped spark plugs and coil from cyl 6 to 1
    • Also replaced spark plugs with new plugs
    • Replaced cyl 6 fuel injector and inspected the electrical connector
    • Confirmed AFR of about 11:1 at the time of the misfire (suggesting the fuel system is keeping up fine since its not leaning out)
    • Removed the ESS manifold and pressure tested to ensure the intercooler wasn't leaking coolant into the cylinder, pressure tested good, held 11psi for over 4 hours. Resealed manifold to head, fresh gaskets, torqued to spec.
    • Compression tested: between 209 and 211 psi across all 6 cylinders
    • Free-rev to 6k RPM, held there, no misfires, it only happens under sustained load
    • Installed M3 motor mounts to match M3 trans mounts
    • Flashed known good tune to the car, still misfires
    • Replaced headers and installed all new hardware and gaskets, confirmed no exhaust leaks


    This misfire problem only started after having the clutch and flywheel replaced. I've driven the car hard all summer and it wasn't an issue until that night on my way home from the shop after the clutch and flywheel install.

    I feel like I've cleared every "real" source of a misfire (fuel is good, ignition is good, air is good), so I'm still thinking the problem has something to do with the detection of the misfire itself.

    I mean, is it possible the new clutch and flywheel combo changed harmonics or something in just the right way that the DME thinks it detects a misfire?

    I'm running a LUK OEM-style dual mass flywheel with a Sachs Performance clutch, and in case it matters I have an ATI super damper on the other end of the crank.

    I've got a thread going on e46f for this issue too, cross-posting for posterity:

    https://forum.e46fanatics.com/showthread.php?t=1242691
    Last edited by rkneeshaw; 04-14-2019 at 11:58 AM.
    2003 BMW 330i ZHP
    ESS Twin Screw Stage 2 - Wavetrac - Headers - Borla - BMW Performance
    Turner Motorsports - Powerflex - Hawk Performance

    Build thread: http://www.zhpmafia.com/forums/showt...yan-s-2003-ZHP
    Wheelwell: 2003 BMW 3 Series
    Fuelly: 2003 BMW 330i

  7. #7
    Join Date
    Jan 2019
    Location
    Tampa, FL
    Posts
    133
    Edit: just read your E46F post. 144k miles.

    How about a leak down test?

    Possible valve float going on at that high RPM due to a weak valve spring?

    Very coincidental about the clutch replacement though. I'm with you on the thinking that maybe it's triggering a knock sensor or something, except that you should experience the same issue free revving at that RPM. Possibly, it is more related to the stiffer M3 mounts you used?

    Deathtrap, did you do any clutch work before this problem started?
    '04 330i ZHP sedan | Mystic blue | Alcantara | 6MT | 111k
    '98 740il | Schwartz 2 | Sandbeige | 5AT | 238k | lowered on Bilsteins w/ B&G springs
    '00 540i sport | Titanium silver | Black | 5AT | 120k
    '85 Mustang GT convertible | Medium charcoal metallic | Gray | 5MT | 215k | one owner, all original

  8. #8
    Join Date
    Dec 2016
    Location
    Boston, MA
    Posts
    562
    Given the coincidence of the misfire happening after the repair, I bet the tech who did the clutch/flywheel replacement unplugged something by accident or didn't properly re-plug a connector somewhere. Or maybe he took it for a joyride afterwards and broke something. Is he a mechanic you trust?

    Funny story; (or not so funny, depending on your perspective) My buddy brought his truck to a shop for repairs, and on the way home he noticed it was running like crap. Next day he started it up and it ran fine. He also noticed his windshield washer fluid light was on. Turns out the mechanic re-connected a vaccum line to his washer fluid reservoir and the engine sucked it dry. Obviously not good for the motor...lucky he didn't blow a head gasket or something. I would have given the mechanic an earful.
    -Chris


  9. #9
    Quote Originally Posted by racer2086 View Post
    Edit: just read your E46F post. 144k miles.

    How about a leak down test?

    Possible valve float going on at that high RPM due to a weak valve spring?

    Very coincidental about the clutch replacement though. I'm with you on the thinking that maybe it's triggering a knock sensor or something, except that you should experience the same issue free revving at that RPM. Possibly, it is more related to the stiffer M3 mounts you used?

    Deathtrap, did you do any clutch work before this problem started?
    That's a negative. My car is bone stock, and the clutch was replaced many years ago according to the Carfax.

    Luckily I have not had this issue reappear since I repaired my ECT sensor harness. Time for some back story...

    FCPEuro had their New Year's sale and I decided to rack up on new parts. Fast forward to a few weeks ago, I removed my intake manifold to tackle all the things under there which includes:

    Removing CCV
    Replacing coolant pipes
    Replacing coolant hoses
    Starter
    TB gasket
    IM gasket
    ECT sensor
    Crank sensor
    Both cam sensors

    Whew. While the car was under the knife I noticed that my fuel injector clips were absent and someone ripped the ECT sensor harness and did a piss poor repair of it. Fixed those things, went to Road Atlanta and had a little hiccup. After that, haven't seen it yet.


    Sent from my Pixel 2 XL using Tapatalk
    2003 Blue ZHP Sedan @ 195k
    Paint chips | Current MIL: P0420 | Airbag Light | Poorly Sprayed Black Style 135s |Ugly Alcantara Steering Wheel | Trunk Squeak | Faded Shadowline Trim
    This car is not a peach. It is a precision instrument, and will be used as such.

  10. #10
    Join Date
    Jan 2019
    Location
    Tampa, FL
    Posts
    133
    Oh, so you solved your problem. And it was electrical related (or so you think) to that bad wiring repair. Interesting.
    '04 330i ZHP sedan | Mystic blue | Alcantara | 6MT | 111k
    '98 740il | Schwartz 2 | Sandbeige | 5AT | 238k | lowered on Bilsteins w/ B&G springs
    '00 540i sport | Titanium silver | Black | 5AT | 120k
    '85 Mustang GT convertible | Medium charcoal metallic | Gray | 5MT | 215k | one owner, all original

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