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  1. #1
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    Cylinder 6 issues?

    Hey guys, just did my plugs, and saw something alarming.

    The first 5 plugs were fine. A grayish color with very little electrode wear. Honestly I think I could have gone quite a while longer on those. Cylinder 6 (closest to the firewall) was alarming.

    This plug was fouled up (completely covered in black soot) and wet oil was all over the threads. I immediately borrowed a compression tester and checked all six cylinders... all six checked out consistently with one another, no issues there. (90-120 psi in each cylinder depending on the crank).

    I installed new plugs, and let the car idle for a few minutes to get up to operating temp (190-200 degrees C). I pulled the cylinder 6 plug and compared to a "good" cylinder and lo behold, it's covered in soot and the threads covered in oil. Pulled the plug out of another cylinder it looks brand new.

    Question is, would this be residual crap getting onto the cylinder or could this be a sign of worse things to come?

    Car has 33k miles, no misfires, no check engine lights, drives normally as far as I can tell before and after the plug change.

    Spoke to my friend who is a BMW foreman, who thinks it's likely blowby from the added stress I put on the car. Anyone else see an issue such as this? It's obvious which one is cylinder 6. And that's wet oil on the threads, not just carbon.

    Click here to enlarge

  2. #2
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    Who did the actual compression test? I have a hard time believing 90-120 is normal, hell having a 30psi swing is bad in itself. However those numbers dont even seem correct. By the looks of it, it might be a ring issue on the 6 cylinder. Or it could simply be an injector issue. A real compression test will let you know.

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    Click here to enlarge Originally Posted by Laloosh Click here to enlarge
    Who did the actual compression test? I have a hard time believing 90-120 is normal, hell having a 30psi swing is bad in itself. However those numbers dont even seem correct. By the looks of it, it might be a ring issue on the 6 cylinder. Or it could simply be an injector issue. A real compression test will let you know.
    How would an injector issue cause the threads to be covered in oil though?

    edit- This is how I did the compression test:
    Compression test:
    1. Pull connectors to all coil packs.
    2. Remove coil pack and spark plug for cylinder to be tested.
    3. Screw in compression gauge.
    4. Turn the engine over until the gauge has leveled out. Might need someone to watch the gauge during cranking if there is not a history on the gauge.
    5. Write down pressure reached next to the cylinder number tested.
    7. Remove compression gauge and replace spark plug and coil pack.
    8. Rinse and repeat for all cylinders.

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    Oil on the threads can simply be a leaking valve cover gasket. As for the compression test, I never did on the car, but on my past cars it involved also pulling the fuel pump relay/fuse and also making sure the throttle is OPEN as my past cars would not care if the gas pedal was floored while cranking, the throttle wouldnt move past its preset settings.

    Pull the coil connection, pull the fuel relay, take off charge pipe and stick broom stick in there or have a buddy hold it open while you crank for 10 or so seconds per cylinder. But like i said, I have never done it on a n54.

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    Loosh is right you need a dry cylinder and open throttle blade and you really need the SAME number of cranks per cylinder for best comparison. Leak down test is better. Are you sure it's oil on the electrode, or fuel? leaky injector may have similar appearance. swap injectors, but need new couplers probably.

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    Click here to enlarge Originally Posted by JoshBoody Click here to enlarge
    Loosh is right you need a dry cylinder and open throttle blade and you really need the SAME number of cranks per cylinder for best comparison. Leak down test is better. Are you sure it's oil on the electrode, or fuel? leaky injector may have similar appearance. swap injectors, but need new couplers probably.
    it's carbon soot on the electrode, definitely oil on the threads. Even my new plug looked exactly the same after 5 minutes of idling.

    the compression gauge I used recalls peak psi. We did multiple cranks and resets, all six read the same depending on the crank. 90 - 120 psi. May not be the most accurate assessment on actual psi, but what it did tell us is that all the cylinders have the same compression.

  7. #7
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    90-120 psi tells you nothing ben. You need the throttle open and then if one is off by more then 10 percent, you got an issue. Just from a common sense point of view, you would expect this engine to be somewhere around 160 at a minimum on all cylinders.

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    If it's not something more serious, it's kinda strange to have 2 issues on the same cylinder: leaky injector and bad VC ring. I would swap injectors 1 and 6, install new plug... don't worry about coding if you can't and run around for couple hundred miles.

    And do better comp test and maybe leak down. and report back

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    Well if the actual boot on the coil that goes on top of the plug is dry and clean and is not oily then it isnt a valve cover gasket issue. The sheer fact that a new plug came back looking like the old one indicates an issue with most likely the injector. Reason I say this is because if he was seeping that much oil past the ring on 6, that car wouldn't be driving the way it does. Then again with a injector that $#@!ed, the same could be said. lol good luck call me if you have questions.

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    The answer is pretty simple actually... Cylinder 6 is just going through a gothic phase.
    Click here to enlarge
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    Click here to enlarge Originally Posted by Laloosh Click here to enlarge
    Well if the actual boot on the coil that goes on top of the plug is dry and clean and is not oily then it isnt a valve cover gasket issue. The sheer fact that a new plug came back looking like the old one indicates an issue with most likely the injector. Reason I say this is because if he was seeping that much oil past the ring on 6, that car wouldn't be driving the way it does. Then again with a injector that $#@!ed, the same could be said. lol good luck call me if you have questions.
    I meant valve cover ring seal... but this would be the minor issue. I had leaky injector once and it was noticeable on start up "sometimes", but driving was fine... unfortunately i didn't check the plug cause I was still under warranty.

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    Click here to enlarge Originally Posted by JoshBoody Click here to enlarge
    If it's not something more serious, it's kinda strange to have 2 issues on the same cylinder: leaky injector and bad VC ring. I would swap injectors 1 and 6, install new plug... don't worry about coding if you can't and run around for couple hundred miles.

    And do better comp test and maybe leak down. and report back
    +1 swapping the injector sounds like the best bet, even just testing at idle once swapped without coding it.

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    I had a test done, I believe specs were supposed to be right around 230? I could be wrong though, and 5% difference is within spec

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    Ben, think you may have seen this before but here's a print out I got from the compression test I had done at the dealer last year...if its oil it might be your valve cover, if its carbon on the plug its most likely your injector...i doubt its a motor issue honestly if you car idles smooth and puts down the numbers it does...i'd just swap the injector from another cylinder and see what happens with the plug in the other cylinder...easy...changing plugs won't hurt either since you already have them

    Click here to enlarge
    Click here to enlarge

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    Click here to enlarge Originally Posted by JoshBoody Click here to enlarge
    I meant valve cover ring seal... but this would be the minor issue. I had leaky injector once and it was noticeable on start up "sometimes", but driving was fine... unfortunately i didn't check the plug cause I was still under warranty.
    There's no valve cover ring seal. There's a valve cover gasket and a leak there will be very visible on the side of the engine coming down into the spark plug hole if it is.

    A really bad leaky injector will cause misfires on cold start, and it'll do it every time if you let the car sit over night to give it enough time to leak into the chamber..
    Click here to enlarge

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    Click here to enlarge Originally Posted by klipseracer Click here to enlarge
    The answer is pretty simple actually... Cylinder 6 is just going through a gothic phase.
    Play some Sisters of Mercy and see if it moves. Click here to enlargeI call injector.

  17. #17
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    Found this thread detailing a valve cover gasket replacement. Sound related to my issue?

    http://www.e90post.com/forums/showth...oil+spark+plug

    Also cylinder 6 plug looks EXACTLY like this guy's issue (too bad the thread had no meaningful advice).

    http://www.e90post.com/forums/showthread.php?t=533247

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    5 out of 5 members liked this post. Yes Reputation No
    When doing a proper compression test you must have all the plugs removed. I looked up the proper prcedure for compresion testing the N54 on ALLDATA. Here is what it says.

    CHECKING ENGINE COMPRESSION USING THE SNAP ON REG; GAUGE SET
    Using the standard Snap On(R) Compression gauge set with the Snap On(R) 12 mm EEPV306A screw in the compression adaptor:
    The vehicle must be at operating temperature.
    1. Remove the cowl assembly.
    2. Remove the engine cover to access the fuel injectors.
    3. [NEW] Remove the fuse that supplies power to the EKP module. Refer to the correct ETM Schematic for each specific vehicle to determine the proper fuse number.
    4. Start the engine and let it run until it stalls.
    5. Remove the electrical connectors from all 6 injectors.
    6. Remove all coils and spark plugs.
    7. Starting with cylinder number one, screw in the EEPV306A adaptor and connect the compression gauge.
    8. Connect the battery charger.
    9. Actuate the starter until the compression stops rising
    10. Repeat steps 7 and 8 for all remaining cylinders.
    11. Record all values and compare to the specification.


    Compression specs for each cylinder is 14-16 bar. With a maximum deviation of all cylinders of 2 bar.

    I hope that helps. Looks like you need to have the car warm and all plugs out. Try it out and let us know. My bet is on injector as well. Swapping the injectors would be the easiest way to test. I'm not sure what the Snap On(R) 12 mm EEPV306A is but maybe look into that also. It may just be a special fitting for our spark plugs?

  19. #19
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    Click here to enlarge Originally Posted by (-(ellblazer420 Click here to enlarge
    When doing a proper compression test you must have all the plugs removed. I looked up the proper prcedure for compresion testing the N54 on ALLDATA. Here is what it says.

    CHECKING ENGINE COMPRESSION USING THE SNAP ON REG; GAUGE SET
    Using the standard Snap On(R) Compression gauge set with the Snap On(R) 12 mm EEPV306A screw in the compression adaptor:
    The vehicle must be at operating temperature.
    1. Remove the cowl assembly.
    2. Remove the engine cover to access the fuel injectors.
    3. [NEW] Remove the fuse that supplies power to the EKP module. Refer to the correct ETM Schematic for each specific vehicle to determine the proper fuse number.
    4. Start the engine and let it run until it stalls.
    5. Remove the electrical connectors from all 6 injectors.
    6. Remove all coils and spark plugs.
    7. Starting with cylinder number one, screw in the EEPV306A adaptor and connect the compression gauge.
    8. Connect the battery charger.
    9. Actuate the starter until the compression stops rising
    10. Repeat steps 7 and 8 for all remaining cylinders.
    11. Record all values and compare to the specification.


    Compression specs for each cylinder is 14-16 bar. With a maximum diviation of all cylinders of 2 bar.

    I hope that helps. Looks like you need to have the car warm and all plugs out. Try it out and let us know. My bet is on injector as well. Swapping the injectors would be the easiest way to test. I'm not sure what the Snap On(R) 12 mm EEPV306A is but maybe look into that also.
    Thanks for the info. we used a proper gauge (12mm adapter) but we did not start the engine and let it run until it stalls. Click here to enlarge I suppose I will need to do the valve cover gasket first, then re-do compression test and get a new spark plug for cylinder 6. Or I suppose I could use an old spark plug in cylinder 6 just to see if it gets wet or not after the valve cover gasket replacement.

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    Yea just re-use one of those other spark plugs. They will be fine for testing purposes. Replace the plug once you have the problem fixed. But from what you describe I think things will be ok. Just frustrating and scary at first.

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    A leakdown test as mentioned earlier is a better idea. Much more accurate and finds 5x more potential problems. I did a lot of them back in the day. LD is also pretty easy to do, you just need an air source. I used to just turn the engine by putting a sockey on an accessory pulley bolt like alternator.

    I'd like to think it would be an injector as the n54 is known to have issues with them but I can't grasp how you could get that much carbon so quickly and it doesn't explain the oil on the plug threads. Did the original #6 plug have caked on layer of carbon like a skin on the electrodes?

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    Click here to enlarge Originally Posted by BavarianBullet Click here to enlarge
    A leakdown test as mentioned earlier is a better idea. Much more accurate and finds 5x more potential problems. I did a lot of them back in the day. LD is also pretty easy to do, you just need an air source. I used to just turn the engine by putting a sockey on an accessory pulley bolt like alternator.

    I'd like to think it would be an injector as the n54 is known to have issues with them but I can't grasp how you could get that much carbon so quickly and it doesn't explain the oil on the plug threads. Did the original #6 plug have caked on layer of carbon like a skin on the electrodes?
    The fouled #6 plug shown in the pic is my original plug.

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    This may sound weird but how did the plug smell? Like fuel or like burnt oil? Can you wipe the oil off or is it caked on there?

    When I zoomed in on the pic it looks as though the wet oily substance is only really on the tip of the plug. Then you have a dry spot in the center of the plug. Then more black towards the back of the plug. Very strange. Almost like there is two issues going on like you said.

    In order for a plug to foul that fast at idle it seems that the only logical thing would be a injector. Hopefully more testing will reveal the problem.

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    Click here to enlarge Originally Posted by (-(ellblazer420 Click here to enlarge
    This may sound weird but how did the plug smell? Like fuel or like burnt oil? Can you wipe the oil off or is it caked on there?

    When I zoomed in on the pic it looks as though the wet oily substance is only really on the tip of the plug. Then you have a dry spot in the center of the plug. Then more black towards the back of the plug. Very strange. Almost like there is two issues going on like you said.

    In order for a plug to foul that fast at idle it seems that the only logical thing would be a injector. Hopefully more testing will reveal the problem.
    I have no idea, but that dry spot may be where the valve cover gasket actually is? If that's the only issue, it's a cheap easy fix. If the issues run deeper, then headaches are coming.

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    Compression tests are fine but if its not misfiring compression is probably normal. Leak down testing would be ideal but is more of a PITA. I'd also peek inside with a scope to look for any signs of fatigue.

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