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Thread: Misfire Cylinder 3 - Among other things

  1. #1
    Join Date
    Jun 2013
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    Alvarado, TX
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    2001 BMW 325i Sedan

    Misfire Cylinder 3 - Among other things

    Good morning all! I want to start off with thanking everyone who has posted about a misfire situation on this forum. I have found a very large amount of information to get me to my current state.

    Background:
    My wife's car was rear-ended so I took the ability to shop around for an older BMW in my area within the price range of the payout from her car being totaled. I settled on the 325i because it drove the best and the gentleman selling the vehicle was giving me a thorough history of what he had done with the car. Mostly to do with the cooling system.

    The vehicle drove fine for a few days, as soon as my wife took it to get registered the alternator went bad. Replaced it, no problems for a few more days. It's at that point (just after registering the vehicle and not passing the emissions test) that I got a check engine light after getting home from work. I drive about an hour home every day from work. It didn't have a problem getting home, but as soon as I turned it back on to run out to the store it stutters, stalls and throws a code. Cylinder 3 misfire with fuel cutoff. If it runs for 5 or so minutes you also get a misfire in cylinder 6. Ficst thing I did was read online and everyone says to swap the coil, so I did. No change, swap spark plug, no change. Even swapped the fuel injector, no change. I did a compression test on each of the cylinders with good results. Between 189 and 191 for each cylinder.

    It's at this point I started looking for a vacuum leak. I found a few parts with rips and tears so I replaced them. Upper and lower intake boot, CCV, and a vacuum hose from the secondary air system. It seems to idle better, but it still throws the misfire code almost immediately after clearing the code and starting the car. I've cleaned the idle air control valve (even though it was moving freely) along with the throttle body and the mass airflow sensor. I'm at a loss as to where to look next. I am waiting on a few parts to finish my smoke machine to test for more vacuum leaks.

    Help:
    My question is, is there a specific place a vacuum leak would cause cylinder 3 and 6 to both misfire? Is there something right in front of my face that I'm not seeing? I have watched every YouTube video and read every forum post google could provide me with information on bmw misfires and I can't imagine what else could be the problem.

    I forgot to mention that I tested the intake and exhaust cam position sensor with a multimeter and a piece of metal and they seem to be working as intended.

  2. #2
    Join Date
    Jun 2013
    Location
    Alvarado, TX
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    2001 BMW 325i Sedan

    2001 325i - Misfire - P1347 & P1353

    Good afternoon fellow BWW enthusiasts!

    Firstly I would like to thank everyone that has posted about a misfire. There is a lot of information out there and I have tried my best to find everything out there in order to assist me before making this post. So thank you to those who have shared their extensive knowledge.

    Background:
    My wife's car was totaled when someone rear-ended her on her way to college orientation. I took the opportunity to give her my current vehicle (a 2017 Tacoma) and get myself a BMW. I enjoy working on cars and I wanted my wife to have a more reliable vehicle as her daily driver, she's also a fan of trucks so it seemed like a win-win. I used the money from the insurance to buy a 2001 325I and I have to say I love it. The car ran great for the test drive and for a few days after that. I took it to get it registered (failed smog but was able to register it on last years pass from the PO). On the way home I got a battery indicator and noticed that the electronics were acting strangely. I put a volt meter to the posts in the engine bay while running and the voltage was all over the place. Put a new alternator in it and it ran great for a few more weeks.

    It's at this point that I got the misfire codes. I drove it home from work (about an hour) without issues, less than 10 minutes later I needed to run to the store and it started up, sputtered a bit, and stalled out. Okay, weird. Misfire. Okay, no problem, I can deal with a misfire. Research. I read everything I could and most of them say "swap coils and plugs to see if the code follows", did the coil first, no change. I did the spark plug next, again no change. Lastly, I changed the fuel injector, no change. Still got a misfire on cylinder 3 and a few minutes later both 3 and 6 (with fuel cutoff).

    Next step was a compression test, 189-191 in all 6 cylinders. Great news, no need to tear the engine apart. But, what could it be? More research led me to suspect a vacuum leak. I started going through each of the common vacuum leak areas and replaced everything I found that needed it. Upper and lower intake boot, vacuum hose from the secondary air system, and the CCV (pain without removing the intake manifold). It idles better, but it's still got the two misfires. If it runs for around 30 or so minutes (to get up to temperature and while I was reading ODB Fusion) it will add a third code for random misfires (0300).

    I'm a bit lost guys, what should I look at next? I am currently awaiting part to build a smoke machine to be able to test for more vacuum leaks. I'm currently using the truck as my daily driver but soon my wife will start classes and I need to get this thing running properly so that it can be my daily driver.

  3. #3
    Join Date
    Jul 2004
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    Ebay has great smoke machines for some $120. For it to be specific to a cylinder you would need a leak right at the intake port, which is unusual.






    For fun, I would ohm test the mosfets on the ecu that drive the ignition coils. Use a multimeter on the feet of the mosfet driver and see if any have significantly different resistance compared to the other 5.

    I have 2 ms43 ecus like yours with misfires due to the mosfets.

    I wouldn't call it common, but if you run out of answers, it may be that, and it's easy to test.

    Also, changing ecu's is not hard on your car.
    -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

  4. #4
    Join Date
    Aug 2010
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    325e 535i M5 325iT 330i
    For the sake of completeness, you might also run a catalytic converter backpressure test to make sure you don't have a clogged cat (or two).

    I chased a similar problem with mine for a long time before I diagnosed a bad cat. Kind of a long shot but a fairly easy test to run, and at worst you will have eliminated them as possible culprits.

  5. #5
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    2001 BMW 325i Sedan
    I did not realize that the forum moderator had to approve the post and thought that my first post must have failed as I was posting from my phone. I apologize for that.

    Thank you both for your reply, I will pull the ECU out when I get home and test that first. I'm not sure how to do the backpressure test so I'll do some research on that and perform that test as well. Hopefully everything for my smoke machine comes in today (all under 30$) so I can see where else I need to replace seals/parts. I did notice that there is an uncovered nipple on the CCV. The one I took out had nothing going to it and as such the new one doesn't either. Is there a hose that needs to be connected here or is it supposed to be plugged?

  6. #6
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    I was able to get the ECU out yesterday and test all but one of the MOSFETs. I wasn't able to get the lead up under the plastic connector. Do you happen to have a layout? Everything I've found says the MOSFETs are for the fuel injectors but I can't find which one correlates to what cylinder. I have not done the backpressure test, I still need to work that one out. Hopefully, when I get home I'll have the time to build that smoke machine, I really want to get it in there so I can find out where else there's a vacuum leak.

  7. #7
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    Quote Originally Posted by themahdii View Post
    I was able to get the ECU out yesterday and test all but one of the MOSFETs. I wasn't able to get the lead up under the plastic connector. Do you happen to have a layout? Everything I've found says the MOSFETs are for the fuel injectors but I can't find which one correlates to what cylinder. I have not done the backpressure test, I still need to work that one out. Hopefully, when I get home I'll have the time to build that smoke machine, I really want to get it in there so I can find out where else there's a vacuum leak.


    ms43 driver rear.jpg

    the last one can be accessed through the back of the board at these points.



    My good ones were all around 14.8-15.0 kiloohm.
    My bad one was 1.50 kiloohm.

    I was told it had spark problems. Either way, if those are not equal, you will have misfires.
    -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

  8. #8
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    Thank you for that, I was able to get them tested. No issues. I'll report back when I get it smoke tested.

  9. #9
    Join Date
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    EXOTICS
    I did notice that there is an uncovered nipple on the CCV. The one I took out had nothing going to it and as such the new one doesn't either. Is there a hose that needs to be connected here or is it supposed to be plugged?
    M54 engine places a rubber cap/plug at that nipple.
    M52 has a vacuum hose connected.

  10. #10
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    Thanks man, I'll cap that off. I found a big vacuum leak at the intake manifold for cylinder 3.


  11. #11
    Join Date
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    Chicago, IL
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    2001 330i and 2005 330i
    That will definitely cause the trouble you're in. Don't go cheap when replacing that part. If it goes in or on your engine, be sure it sports a roundel. Knock-off parts will fail prematurely.
    Johnny Murray

  12. #12
    Join Date
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    Quote Originally Posted by 328 Power 04 View Post
    For it to be specific to a cylinder you would need a leak right at the intake port, which is unusual.




    Quote Originally Posted by themahdii View Post
    Thanks man, I'll cap that off. I found a big vacuum leak at the intake manifold for cylinder 3.


    I have never seen a blue manifold gasket... They're all orange and last forever.
    Good find!
    -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

  13. #13
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    2001 BMW 325i Sedan
    Yeah, it looks like a felpro. Definitely running better and there are no codes. I think it was a PO installation error rather than amgasket fail, but who knows. I got the oem orange one and it's running great. Now to source a headlight as its melted. Thanks again to everyone for their suggestions. I am very pleased we got it working again.

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