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Thread: Cylinder 6 misfire woes

  1. #26
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    Code reads always have freezeframe data, and depending on the tools used you can get a lot of information.

    I prefer using a tool capable of reading the BMW manufacturer codes and using the freeze frame under which it happened.
    -Abel

    - E36 328is ~210-220whp: Lots of Mods.
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  2. #27
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    Actually this may be important information I should reiterate....

    About the last 5 times that cylinder 6 totally died and I got P0306, I've rebooted the ECU using this method from the BMW Doctor https://www.youtube.com/watch?v=1Owjx2I1jZw:
    • Disconnect battery
    • Touch the battery cables together for 15 seconds
    • Turn on headlights
    • Wait 15 minutes or more
    • Put everything back together and start the car
    • Clear the code with my Bluedriver OBD reader.


    Then the car runs really great, like track ready. I've gone WOT and taken it up to 80mph on the highway and it just zings. So far, I've gone anywhere from 10 to 150 miles with no code. Then cylinder 6 dies and the code comes back soon after a cold start. Since I know the car CAN run great, I'm wondering if it is indeed an ECU issue.

    Does that help?
    Last edited by Z3J1; 11-11-2022 at 12:48 PM.

  3. #28
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    Quote Originally Posted by Z3J1 View Post
    DME MS42. Trying to see if it’s causing the cylinder 6 misfire. So what exactly am I looking for?!
    Damn. Seriously would not expect to open it up and get down to the component level.
    You’re not going to see anything without the correct diagnostic equipment.

    I was interested in the connector terminals. Where it plugs into the wiring harness.


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  4. #29
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    Quote Originally Posted by magnetchief View Post
    Damn. Seriously would not expect to open it up and get down to the component level.
    You’re not going to see anything without the correct diagnostic equipment.

    I was interested in the connector terminals. Where it plugs into the wiring harness.
    Doh. That makes much more sense! Those connector terminals looked clean as a whistle.

  5. #30
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    Quote Originally Posted by Z3J1 View Post
    Actually this may be important information I should reiterate....

    About the last 5 times that cylinder 6 totally died and I got P0306, I've rebooted the ECU using this method from the BMW Doctor https://www.youtube.com/watch?v=1Owjx2I1jZw:
    • Disconnect battery
    • Touch the battery cables together for 15 seconds
    • Turn on headlights
    • Wait 15 minutes or more
    • Put everything back together and start the car
    • Clear the code with my Bluedriver OBD reader.


    Then the car runs really great, like track ready. I've gone WOT and taken it up to 80mph on the highway and it just zings. So far, I've gone anywhere from 10 to 150 miles with no code. Then cylinder 6 dies and the code comes back soon after a cold start. Since I know the car CAN run great, I'm wondering if it is indeed an ECU issue.

    Does that help?
    Yeah so I would stop doing that and I'd get proper diagnostic equipment. It isn't hard or expensive to set INPA up

    Going into my TENTH YEAR of providing high quality reproduction BMW fabrics!

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  6. #31
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    Quote Originally Posted by Z3J1 View Post
    Actually this may be important information I should reiterate....

    About the last 5 times that cylinder 6 totally died and I got P0306, I've rebooted the ECU using this method from the BMW Doctor https://www.youtube.com/watch?v=1Owjx2I1jZw:
    • Disconnect battery
    • Touch the battery cables together for 15 seconds
    • Turn on headlights
    • Wait 15 minutes or more
    • Put everything back together and start the car
    • Clear the code with my Bluedriver OBD reader.


    Then the car runs really great, like track ready. I've gone WOT and taken it up to 80mph on the highway and it just zings. So far, I've gone anywhere from 10 to 150 miles with no code. Then cylinder 6 dies and the code comes back soon after a cold start. Since I know the car CAN run great, I'm wondering if it is indeed an ECU issue.

    Does that help?
    For what it's worth, ecu reboot is complete nonsense (on this ecu and modern ecus) and findings after are coincidental. This is because this ecu stores all the data in non-volatile memory that doesn't erase when power is off.

    - - - Updated - - -

    It certainly isn't a diagnostic test.
    -Abel

    - E36 328is ~210-220whp: Lots of Mods.
    - 2000 Z3: Many Mods.
    - 2003 VW Jetta TDI Manual 47-50mpg
    - 1999 S52 Estoril M Coupe
    - 2014 328d Wagon, self-tuned, 270hp/430ft-lbs
    - 2019 M2 Competition, self-tuned, 504whp
    - 2016 Mini Cooper S

  7. #32
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    "But the guy on uTube said".... I must hear that ten times a day now in this new job. And that's from professional mechanics, errr, techs. Listen, advice from some random guys on a forum in the backwaters of the internet is vastly superior to some self-important random on utube. Believe them Seimens DMEs are not "rebootable" with the three handed tap the cables together three times voodoo like a Cheby. The only thing you do is reset the radio. "Doctor BMW" indeed.

    A bit more info for the detective work. The code doesn't set when the engine running goes to crap. The DME sees an issue (which may be minor), flags it, sets the code, and turns off the offending cylinder. *that* is when the engine running goes to crap. So you are looking for the problem at or just before code setting, not after. Freeze frame data is the key for this, OBD2 or BMW, doesn't matter to me.

    Fun Fact 3. The OBD2 standard was lifted directly from the BMW / VW / Seimens K-Line diagnostic system. And it would have been quite simple and effective if Ford and GM hadn't gotten a rash of "not invented here"s and demanded their own protocols included.
    Last edited by rf900rkw; 11-11-2022 at 04:11 PM.


    /.randy

  8. #33
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    Quote Originally Posted by BimmerBreaker View Post
    Yeah so I would stop doing that and I'd get proper diagnostic equipment. It isn't hard or expensive to set INPA up
    I use this too. Followed the following to get it set up on an old laptop.


    The Z3 Diagnostics Thread: Instructions, Experiences, Discussions, Experimentation
    https://r.tapatalk.com/shareLink/top...ink_source=app


    Sent from my iPhone using Tapatalk

  9. #34
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    Quote Originally Posted by rf900rkw View Post
    advice from some random guys on a forum in the backwaters of the internet is vastly superior to some self-important random on utube.
    Understood. I try to triangulate my sources. And I truly appreciate the wealth of knowledge being shared here, which is why I'm here!

    Quote Originally Posted by rf900rkw View Post
    The code doesn't set when the engine running goes to crap. The DME sees an issue (which may be minor), flags it, sets the code, and turns off the offending cylinder. *that* is when the engine running goes to crap.
    Turns off the cylinder? You're saying that the computer sees P0306 and says "it's better to shut her down". That is interesting... and helpful... assuming I can trust some random guy on a forum

  10. #35
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    Quote Originally Posted by Z3J1 View Post
    Turns off the cylinder? You're saying that the computer sees P0306 and says "it's better to shut her down". That is interesting... and helpful... assuming I can trust some random guy on a forum
    Yes the DME itself will shut down the cylinder if misfires are detected, in my case with the bad E90 DME I did get specific DME Firing, Ignition coil, and combustion codes for the offending cylinder beyond/instead of the 'simple' P030x misfire codes - I would speculate if you are NOT getting some OTHER DME codes it is probably not your DME - at least from my experience.

    Z3 Pro Life Tip, If you are going to listen to some random guy on this Forum - it would be best if they are a 'Randy'

    “Great wisdom is generous; petty wisdom is contentious.” 无为

  11. #36
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    That is interesting... and helpful... assuming I can trust some random guy on a forum
    Randy's been offering expert advice here, not for years, but for decades. I hope he doesn't take offense.
    Claude Berman, 96 Z3 Production Date 2/96 BMW CCA# 581686
    The only good is knowledge and the only evil is ignorance. Socrates, 469–399 B.C.E

  12. #37
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    Quote Originally Posted by cyberman View Post
    Randy's been offering expert advice here, not for years, but for decades. I hope he doesn't take offense.
    Your quote doesn’t provide the context that “some random guy on a forum” are his words nor does it show my so I trust he sees the humor As I research this forum, I definitely see his words are gold! All respect to him and others who are so willing to freely share such hard earned wisdom.
    Last edited by Z3J1; 11-12-2022 at 10:23 AM.

  13. #38
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    so willing to freely share such hard earned wisdom.
    If Randy and Abel had a dollar for every helpful post they've made, well they could retire in style.
    Claude Berman, 96 Z3 Production Date 2/96 BMW CCA# 581686
    The only good is knowledge and the only evil is ignorance. Socrates, 469–399 B.C.E

  14. #39
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    Quote Originally Posted by cyberman View Post
    If Randy and Abel had a dollar for every helpful post they've made, well they could retire in style.
    And of course you should add Randy Forbes. Make it a threesome!

  15. #40
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    Quote Originally Posted by Z3J1 View Post
    Turns off the cylinder? You're saying that the computer sees P0306 and says "it's better to shut her down". That is interesting... and helpful... assuming I can trust some random guy on a forum

    It's in the BMW documentation. But then you would be trusting some random PDF from the interwebs.

    In theory it can set a P030x code for a very light misfire without killing the cylinder. But it doesn't happen. A little stutter and wham, you suddenly shake and sound like a Harley. They do this to keep from pumping raw fuel into the cat, which would cause an overheat and the cat substrate to melt and clog. Visualize a world where Chevy and Ford put these few extra lines of code in their controllers. No melted cats. No aftermarket cat market. No market for sawz-alled exhaust parts.


    /.randy

  16. #41
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    Quote Originally Posted by cyberman View Post
    Randy's been offering expert advice here, not for years, but for decades. I hope he doesn't take offense.

    That guy is gone. Walked out the door and didn't look back. Didn't even take his toolbox with him. I'm just some random putz with a bit of extra time while working some mundane job in... (checks current ORG chart) Sales and Public Relations. Yep, me. Sales. And Public Relations. At the same time. Together, even. When that org chart came out.... I ran out of emojis. I hadn't laughed that hard or long since seeing Blue Velvet.


    /.randy

  17. #42
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    Yep, me. Sales. And Public Relations. At the same time. Together, even. When that org chart came out.... I ran out of emojis. I hadn't laughed that hard or long since seeing Blue Velvet.
    Elon recently let him go from Twitter.
    Claude Berman, 96 Z3 Production Date 2/96 BMW CCA# 581686
    The only good is knowledge and the only evil is ignorance. Socrates, 469–399 B.C.E

  18. #43
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    Last edited by z3forlife; 11-13-2022 at 10:06 PM.

  19. #44
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    Quote Originally Posted by rf900rkw View Post
    In theory it can set a P030x code for a very light misfire without killing the cylinder. But it doesn't happen. A little stutter and wham, you suddenly shake and sound like a Harley. They do this to keep from pumping raw fuel into the cat, which would cause an overheat and the cat substrate to melt and clog.
    This raises another factor I've been meaning to ask about... Is it feasible a muffler delete could be causing my cylinder 6 misfire and shutdown?

    This car came to me lowered and loud (though I must admit I like the exhaust tone). After a cold start, it certainly takes a little time to warm up and smooth out and it's during this time that the code typically shows up.

  20. #45
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    Update: I hope to provide some freeze frame or diagnostic info. For now I noticed a couple new things. Is it possible one of these is causing cylinder 6 to misfire? I should add the last time I checked my obd reader, it showed a pending trouble code for a cylinder 2 and 3 misfire.

    1. Smoke test revealed no major leaks but there was a very tiny leak where the intake boot meets the throttle body and IACV.

    2. The photo shows a big hole on this hose (along the valve cover), which I believe is connected to an air pump.
    Attached Images Attached Images

  21. #46
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    Quote Originally Posted by Z3J1 View Post
    1. Smoke test revealed no major leaks but there was a very tiny leak where the intake boot meets the throttle body and IACV.
    Yes a vacuum leak can cause a misfire, the engine also moves when running which can cause it to pull at the boot, opening the "small" tear. Remove the boot and inspect it, if it is torn or cracked replace it, otherwise just re-seat it and ensure it seats on the throttle body correctly.

    Second photo shows the SAP valve, the hose leading to it has deteriorated, this could cause SAP codes, but not misfire codes as the valve will be closed once at operating temperature. I would start by fixing the leak you observed with the smoke test and going from there.

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  22. #47
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    The DME for my car was inexpensive on eBay and it did fix a recurring CEL about an O2 sensor. So, DMEs can fail. Check the cost of one for yours - it may be worth a shot, and hey, good idea to have one on the shelf because eventually the supply will dry up.
    Claude Berman, 96 Z3 Production Date 2/96 BMW CCA# 581686
    The only good is knowledge and the only evil is ignorance. Socrates, 469–399 B.C.E

  23. #48
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    A vacuum leak will affect all cylinders sharing that plenum. In this case, all six. Same goes for an air leak in the exhaust. If the leak is close enough to the head to screw with the O2 reading, it will affect all three cylinders sharing that O2.


    The MS42 DME is irrevocably married to the vehicle. You can not swap them between vehicles like you could the earlier designs. To break the satanic bonds tying the DME to it's master EWS requires skill set Abel.


    /.randy

  24. #49
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    Quote Originally Posted by Z3J1 View Post
    Update: I hope to provide some freeze frame or diagnostic info. For now I noticed a couple new things. Is it possible one of these is causing cylinder 6 to misfire? I should add the last time I checked my obd reader, it showed a pending trouble code for a cylinder 2 and 3 misfire.

    1. Smoke test revealed no major leaks but there was a very tiny leak where the intake boot meets the throttle body and IACV.

    2. The photo shows a big hole on this hose (along the valve cover), which I believe is connected to an air pump.
    If you look to the right of where you circled your hole on the Secondary Air pump hose, there is a black vacuum hose that connects to the EGR valve. This vacuum line will deteriorate and break apart right at the EGR valve.This hose runs along the manifold, behind the engine block and connects to the intake manifold side on the passenger side. Make sure hose is not broken or it will cause Codes during startup and rough starts.

  25. #50
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    Freeze frame from my Bluedriver OBD reader. Any clues in there?

    - Cleared last CEL.
    - Drove 10 miles. No problem.
    - Shut engine off and waited 2 hours.
    - P0306 came up about a minute after starting. Cylinder 6 did not shut down like in the past, but I let it idle only for a few minutes.
    Attached Images Attached Images
    Last edited by Z3J1; 11-23-2022 at 05:59 PM.

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