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Thread: 540i multiple misfire when warmed up, runs well when cold, UPDATE THREAD.

  1. #1
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    540i multiple misfire when warmed up, runs well when cold, UPDATE THREAD.

    SOLVED (see recent post or bottom of this first post).

    Ok, I've done some more troubleshooting on my engine misfire on my 540. I'll try to lay out what I know so far.

    About two months ago I got a flashing CEL light that turned solid after about 15 seconds. I pulled the codes and got the random/multiple misfire code and also codes for two separate cylinders. I originally thought it was cylinder 1 and 6. Looking at my notes, I now believe that it was originally 1 and 5. This is important because at one point I switched coils between 5 and 6, and I thought the misfire moved, but in reality I think it was always on cylinder 5 and it did not move.

    I did some troubleshooting with regards to switching coils and boots with no result (I now believe, see above). I also repaired what appeared to be a vacuum leak. There was no change. Except that the cylinder 1 misfire vanished, and has not returned.

    When the car is cold, it drives very well, it takes abut 15-20 minutes of driving before it starts missing again. I discovered that if I drove the car carefully, without lugging it too much or putting much load on the engine, I could make my entire 30 minute commute, and then 8 hours later I could drive home, and have no missing/no codes. It was pretty cold out during this time, and I now think that has a lot to do with it.

    So I drove it carefully for a while with no missing. When the coils I ordered came in, I took it for a drive to try to get it to start missing, and had no luck. It ran perfectly, and has for the last few weeks. It has been cold.

    Last week it started missing again. THIS TIME, I get the random/multiple misfire code, and a code for cylinder 2, which I have never had before. Cylinder 1, 5 and 6 are all fine. I am not sure what the outside temp was, as I had not made the connection at that time that the temperature had a direct impact on my misfire. The nest day was cold, and it ran fine to and from work. The next day was warm, and it started missing 15 minutes into my drive.

    I switched coil and boot around today, and the miss did not follow. I also disconnected the MAF, with no change. I also went around the engine bay with an open unlit propane torch, with no result.

    I pulled the plug for cylinder 2, and it looks like this:



    So where do I go from here? I have read the O2 sensors and CPS sensors can cause a misfire when warm (PO says CPS was replaced 10k ago). And it certainly feels like it could be happening when the pipes get hot. But that doesn't really explain the misfire across banks (indicates vacuum leak possibly), and I get no codes with my peake for either of those items. Can they fail without a code?

    Here is my original thread: http://www.bimmerforums.com/forum/sh...have-questions

    Thanks for any help!


    Also: different subject, but at one point today, my heater valve/secondary water pump (one unit, correct?) was emmitting a pretty loud humming noise and vibrating, after I had turned the car off. this continued for several minutes until I turned the key to position 2. It did not reappear that I noticed. Problem?


    Little bit of an update...


    Today I changed the plugs out for 8 new NGK BKR6EQUP. 6 of the remaining 7 besides the one I took a picture of were pretty nasty. Cylinder #8 had a decent amount of oil coating the threads. Didn't seem to be much of anything on the head of the plug. There was no change in the operation of the engine after the spark plug change, still random/multiple misfire, and misfire in cylinder 2.


    I also did a compression test. I do not know that the gauge is accurate. I was only able to tighten the gauge by twisting the hose, so I don't know if being able to get it tighter might increase the results. I got 150 PSI across all cylinders +/- 5. I was wondering if there was still some oil in cylinder #8, making it a wet test. Seems possible.


    I did remove the DME relay. I did not press the gas pedal down. The car cranked very slowly while I did the test. Normal?


    Regarding my mystery buzzing heater relay/pump, I turned on the REST mode to see if that was it. With REST turned on, the fan is active. That was not the case before. So I dunno there.


    Friday I will get a back pressure tester in the mail, and I will perform that test.
    Given my symptoms (miss at low RPM when warmed up, runs fine when cold, and/or above 2500 RPM), and the research I have done, I do not expect to find excess back pressure as my symptoms are not really consistent with what I have read for cat failure. However, some very knowledgeable people have told me to do the test, so I will, and be glad to eliminate that cause, either way.

    =======================================

    =======================================

    FINAL UPDATE (hopefully):

    So yesterday O'Reilly's scanner reported cylinder 5 misfiring, not 2, as my Peake did. As I was thinking last night, I remembered that when I switched out my spark plugs, I noticed that the coil for cylinder 2 was not a "BMW" labeled Bremi coil (as were all other coils on my car), but looked like this:



    I didn't think anything of it, as the Peake showed a miss for cylinder 2, not 5. but after I realized that it was in fact on the same coil as my misfire, I switched it out for a new Bosch, and it has been fine all day. I hate to jinx myself, but I think that was it.

    The only thing I can think of is that the Peake reads the cylinder sequence as:

    7-------------8
    5-------------6
    3-------------4
    1-------------2

    While other scanners read the correct sequence:,

    4-------------8
    3-------------7
    2-------------6
    1-------------5

    Making 2 and 5 the same cylinder. That's all I can think of, but I don't remember reading that warning regarding the Peake at any time.

    The bad coil has the same body as the Bremi, is it an off brand, or what?

    Thanks to everyone for their help.
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    Last edited by five40eye; 03-13-2015 at 07:06 PM.

  2. #2
    JimLev's Avatar
    JimLev is offline Artifically Aspirated Moderator
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    Have the intake manifold gaskets ever been changed?
    Did you ever get a back pressure test done for the CAT's?

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    Quote Originally Posted by JimLev View Post
    Have the intake manifold gaskets ever been changed?
    Did you ever get a back pressure test done for the CAT's?
    I only have the records for the one owner before me, but none of the records I have indicate that the intake manifold gaskets were changed.

    I have not had a back pressure test done yet, I was trying to do what I can myself before paying someone else to work on it, but I should have that done. Probably foolish to continue without eliminating that. I will try to get that done soon and let you know the results. By the same token, I should probably have a smoke test done. That would show a leak on the intake manifold gasket, yes?

    Thanks Jim.

    Edit: Would you say it is consistent with cat failure to run fine till quite warm?
    Last edited by five40eye; 03-10-2015 at 10:24 AM.

  4. #4
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    Little bit of an update...


    Today I changed the plugs out for 8 new NGK BKR6EQUP. 6 of the remaining 7 besides the one I took a picture of were pretty nasty. Cylinder #8 had a decent amount of oil coating the threads. Didn't seem to be much of anything on the head of the plug. There was no change in the operation of the engine after the spark plug change, still random/multiple misfire, and misfire in cylinder 2.


    I also did a compression test. I do not know that the gauge is accurate. I was only able to tighten the gauge by twisting the hose, so I don't know if being able to get it tighter might increase the results. I got 150 PSI across all cylinders +/- 5. I was wondering if there was still some oil in cylinder #8, making it a wet test. Seems possible.


    I did remove the DME relay. I did not press the gas pedal down. The car cranked very slowly while I did the test. Normal?


    Regarding my mystery buzzing heater relay/pump, I turned on the REST mode to see if that was it. With REST turned on, the fan is active. That was not the case before. So I dunno there.


    Friday I will get a back pressure tester in the mail, and I will perform that test.
    Given my symptoms (miss at low RPM when warmed up, runs fine when cold, and/or above 2500 RPM), and the research I have done, I do not expect to find excess back pressure as my symptoms are not really consistent with what I have read for cat failure. However, some very knowledgeable people have told me to do the test, so I will, and be glad to eliminate that cause, either way.

  5. #5
    JimLev's Avatar
    JimLev is offline Artifically Aspirated Moderator
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    You should have wedged the TB wide open when you did the compression test.
    With the DME relay out the throttle could be non functional.
    Not sure why the engine turned over slowly, maybe a weak battery?

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    Quote Originally Posted by JimLev View Post
    You should have wedged the TB wide open when you did the compression test.
    With the DME relay out the throttle could be non functional.
    Not sure why the engine turned over slowly, maybe a weak battery?

    Yeah I messed up on that. The manual says to press on the pedal, but I didn't figure it would do anything with the drive-by-wire system. Would that raise or lower my numbers? I am also not sure if it was warmed up all the way, KTMP of probably 80C. I botched it, ha.

    The slow turn-over was strange. I disconnected the DME relay and cranked it and it was totally normal. Then I pulled out all the coils and plugs, screwed in the gauge, and cranked it and it was slow. Very slow, like 2 rotations per second. Then I put it back together and it was fine. No code even for the DME.

  7. #7
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    Compression would be a bit higher with TB open.
    With all plugs out it should have spun pretty fast.

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    Quote Originally Posted by JimLev View Post
    Compression would be a bit higher with TB open.
    With all plugs out it should have spun pretty fast.
    Yeah I know, it was bizarre. I'll not worry about the compression I guess, 150 isn't horrible (not great through), and it sounds like it's actually a little higher.

    Thanks.

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    I think I'm gonna lose my mind...I went by O'reilly's after work, and had them pull the codes. Right before I went in, I scanned with my peake to make sure the port was functional (O'Reilly's scanner did not work when I went in this morning). I got the same codes I have been getting the past few weeks, "multiple/random misfire" and "misfire cylinder two". When the guy at O'Reilly's scanned it, the only code their Bosch scanner returned was P0305. That's a completely different cylinder than the Peake!


    Is the Peake a total piece of s#!t, or what the heck could cause it to throw a code for 2 and not 5 on the Peake, and for 5, and not 2, on the Bosch??


    Thanks.

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    Final update (hopefully):

    So yesterday O'Reilly's scanner reported cylinder 5 misfiring, not 2, as my Peake did. As I was thinking last night, I remembered that when I switched out my sparkplugs, I noticed that the coil for cylinder 2 was not a "BMW" labeled Bremi coil (as were all other coils on my car), but looked like this:



    I didn't think anything of it, as the Peake showed a miss for cylinder 2, not 5. but after I realized that it was in fact on the same coil as my misfire, I switched it out for a new Bosch, and it has been fine all day. I hate to jinx myself, but I think that was it.

    The only thing I can think of is that the Peake reads the cylinder sequence as:

    7-------------8
    5-------------6
    3-------------4
    1-------------2

    While other scanners read the correct sequence:,

    4-------------8
    3-------------7
    2-------------6
    1-------------5

    Making 2 and 5 the same cylinder. That's all I can think of, but I don't remember reading that warning regarding the Peake at any time.

    The bad coil has the same body as the Bremi, is it an off brand, or what?

    Thanks to everyone for their help.
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    Last edited by five40eye; 03-13-2015 at 07:06 PM.

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    Glad you got it worked out!

    Forgive me for getting OT.

    Jim, I thought moving the throttle body can mess up adaptions or something. I was under the impression that moving the TB on drive by wire can mess something up. Thoughts?


    Quote Originally Posted by JimLev View Post
    You should have wedged the TB wide open when you did the compression test.
    With the DME relay out the throttle could be non functional.
    Not sure why the engine turned over slowly, maybe a weak battery?

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    misfiring

    Quote Originally Posted by collardgreens View Post
    Glad you got it worked out! Forgive me for getting OT. Jim, I thought moving the throttle body can mess up adaptions or something. I was under the impression that moving the TB on drive by wire can mess something up. Thoughts?
    I have the same problem on my 6L -525 : I spotted quickly it was heat related as I'm in Florida... cold start ok for 20 minutes, then trouble.....let it cool down and good to go for another 20 .My mechanic blaims it on the computer as technically he can't find anything wrong ( cables, plugs, coils, sensors...).PLEASE LET E KNOW IF YOU FIND OUT WHAT CAUSES IT EXACTLY ???? I'm putting in a new ecu/ dcm unit this week just to get an exact READING of the codes.tx!

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    extra info : my mechanic wanted me to do a remapping of the ecu/ dcm unit by BMW before doing any repairs , and a exact read out on the codes afterwards -
    as he had no clue WHAT to replace at all. So with the new dcm, we hope to get a new exact read out without FALSE CODES.

  14. #14
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    Quote Originally Posted by xlvvrk View Post
    I have the same problem on my 6L -525 : I spotted quickly it was heat related as I'm in Florida... cold start ok for 20 minutes, then trouble.....let it cool down and good to go for another 20 .My mechanic blaims it on the computer as technically he can't find anything wrong ( cables, plugs, coils, sensors...).PLEASE LET E KNOW IF YOU FIND OUT WHAT CAUSES IT EXACTLY ???? I'm putting in a new ecu/ dcm unit this week just to get an exact READING of the codes.tx!
    Unbelievable.

    1. this thread is from 2015.
    2. this thread is for a very different engine.
    3. you're quoting some replier-to-OP who's talking about throttle body questions, not the original poster... yet your comment seems to talk about OP
    4. OP says clearly above that the problem was a BAD COIL and explains how he missed it because of blah blah cylinder numbers, so he "FOUND OUT WHAT CAUSED IT EXACTLY" if you only use your eyeballz and presumed ability to read.
    5. do you have the slightest idea what you're doing with a replacement "DME" (BMW for "ECU" nobody remotely calls them "ECM" or "DCM"...) ? you cant just toss a used one in the car it will never start it. immobilization etc.

    Suggest you stick to your own thread instead of posting in dead threads that aren't related to your issue. I'll post in that thread in a minit too and tell you all the things you've done wrong there too...
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