Results 1 to 2 of 2

Thread: Misfire under load

  1. #1
    Join Date
    Aug 2018
    Location
    Rochester
    Posts
    22
    My Cars
    2004 BMW M3 Coupe

    Misfire under load

    2004 m3, did a full rebuild last year, and up until this point I've had no issues. Slowly a cylinder 1 misfire has developed, but strangely it's only under certain load. It developed somewhat progressively, a few days after first feeling it slightly, it got bad.

    Usually the issue shows itself at low rpm/high load, or at any really high throttle. I can feel when it happens because there's a complete cutout of power, and the vibration is noticable. A few times, I've had it happen immediately after startup, at idle it's misfiring. Turning the car off and back on fixes it somehow. It typically doesn't throw a CEL, but occasionally it will and the only code is for a cylinder 1 misfire. When it does throw a code, it'll disable cylinder 1 completely. I had a scanner hooked up and was looking at the "number of deactived cylinders" under the fuel system live data, and when I could feel the bogging it showed that all 6 cylinders were deactivated. Not sure how accurate that is, but what it tells me is that there's a fuel cut happening due to something, possibly the misfire in cylinder 1.

    So far I've replaced fuel filter, pump, pressure regulator, checked the spark plug (looks perfect, only 3k miles on it), ran a vanos test (the adjustment range is good but the time to adjust is slow). I've also checked compression and it was at 180psi. I've tried resetting fuel trims and reseating the intake boot, to no avail. Typing this now I realize it could be something wrong with the ITB or the intake boot could cause this. That'll be what I check next.

    If anyone has ideas as to what I should try and diagnose next I'd love some pointers.

  2. #2
    dworthy's Avatar
    dworthy is offline Wagon meister :) BMW Tech Expert
    Join Date
    Nov 2010
    Location
    Grafenwoehr, Germany
    Posts
    14,483
    My Cars
    16 220i 05 325it 05 M3
    Sometimes missfires will show up when you have a vacuum leak oddly enough. I would wonder if the intake gasket on cylinder #1 is pinched, or perhaps the boot from the plenum isn't seated properly. Do a visual check first of course, and if you don't see anything I would see about getting the intake smoke tested.
    Darin
    Current:
    16 220i Active Tourer Platinsilver MET (C08)/Dakota Black (PDSW), P7ACA, P7LDA, P7LHA, P9BDA, 6sp Manual - Wife's new toy!
    05 325it Electric Red(438)/Gray(N6TT) ZCW, ZSP 5sp Manual Back set cover, trunk mat, Euro Infra-Rot front windshield, and mud flaps! Mr. Wagon My new Winter car.
    05 M3 Imolarot II(405)/Gray(N5TT) ZCW, ZPP 6sp Manual C.F. Lip, CSL diffuser, SSK, Euro Infra-Rot front windshield and a trunk liner! Mr. Go_Fast Stored for the Winter
    Past:
    95 318is Montreal Blue Met (297)/Beige(K1SN) RIP, killed by an Idiot.
    84 M535i gray market Burgandy Rot Met/Black Leather Lowered by Intrax on bilies, poly everywhere, B&B cat back system, K&N, and a hitch! Da Beast - Still running w/400k+!
    91 316i euro Tizianrot/Gray cloth - E-36 w/M-40 RIP, but great on gas! Best was 38 MPG
    82 528i euro Saphire Blue Met/Blue Leather RIP
    79 525 euro Green/Green RIP
    79 318 Silver/Black - The first one that got it all started
    M-Flight Member

Similar Threads

  1. Misfire under load 530i
    By jregier in forum 1996 - 2003 (E39)
    Replies: 11
    Last Post: 09-24-2019, 07:54 PM
  2. Terrible misfire under load
    By 5OnTheFloor in forum 1991 - 1999 (E36)
    Replies: 27
    Last Post: 01-01-2013, 05:21 AM
  3. Misfiring under load
    By Matt190 in forum 1976 - 1989 (E24)
    Replies: 2
    Last Post: 08-09-2012, 12:24 PM
  4. misfires under load
    By pgallagh123 in forum 1992 - 1999 M3 (E36)
    Replies: 13
    Last Post: 03-02-2010, 10:53 PM
  5. Misfire under load.
    By Alecs MacDonald in forum 1991 - 1999 (E36)
    Replies: 1
    Last Post: 10-10-2008, 01:43 AM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •