V8 n62 engine analysis by slow motion sound - Bimmerfest - BMW Forums



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X5 E70 (2007 - 2013)
E70 BMW X5 produced between 2007 and 2013. Discuss the E70 X5 with other BMW owners here.

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  #1  
Old 09-04-2019, 05:06 AM
deroy deroy is offline
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V8 n62 engine analysis by slow motion sound

2007, 165k miles V8. No codes, running smooth. But still chasing the root cause of a darker than the others spark plug on cylinder 3 and some mild vibration.

I did something out of the ordinary; I took some slowmotion clips along both cylinder banks. I can identify a ‘ding’ (note that that is in slowmotion sound). Listen well; It’s faintly audible BETWEEN two igintions in the right bank (With red battery tab) and more clear spot ON an ignition in the left bank clip. By analysing the firing sequence and listening well to the firing pattern I can pin it to my suspect cylinder 3, or 6 in terms of the firing sequence.

In real time sound that ding will sure be a much higher frequency click or tick or so. But I have no idea what to make of it. Is it evidence of a weak spark? A richer or leaner burn pointing more towards an injector? Something more mechanical in the valvetrain or crankshaft?

https://drive.google.com/file/d/11fZ...w?usp=drivesdk

https://drive.google.com/file/d/1QhB...w?usp=drivesdk



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  #2  
Old 09-04-2019, 08:06 AM
B4_685 B4_685 is offline
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Mein Auto:
Thats so cool to listen to - you can hear the lower cylinder firing noises in the background - the rest sounds like valvetrain and timing chain - interesting to know whats what tho...


N63 E70 X5 2012
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  #3  
Old 09-04-2019, 08:45 AM
2010xdrive35d's Avatar
2010xdrive35d 2010xdrive35d is online now
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I'm going home tonight to try this on my d. Man I bet that sounds cool. You've inspired me lol

Hope you get yours figured out.
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Old 09-04-2019, 09:34 AM
Gary214 Gary214 is online now
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I heard Elvis Presley
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Old 09-04-2019, 11:26 AM
deroy deroy is offline
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Mein Auto: X5 e70 4.8
for fellow V8 owners:
firing order as found on the web:
15486372

Split between passenger side (1-4, left column below) and drivers side (5-8, right column) you get:

1 fire pause
pause fire
fire pause
pause fire
pause fire
fire (3) pause
pause fire
fire pause
1 fire pause
pause fire
fire pause
pause fire
pause fire
fire pause
pause fire
fire pause
etc.

By cueing in on the double fire on each side, 4 and 5 on the right, 1 and 8 on the left, you can pin the ignitions you hear in the clips to individual cylinders. I guess that'll be hard on an inline 6.

Last edited by deroy; 09-04-2019 at 11:30 AM.
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Old 09-05-2019, 10:02 AM
gcguru gcguru is offline
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Can you repost audio of it at normal speed. Left vs right. And also while lightly tapping the throttle off-idle, quick taps...?

At this point I know the plugs are new, did you check the gaps?
Did you read the individual 8 coils resistance off the scanner as mentioned earlier?

If this is a harmonic/vibration while not in gear, it may not have anything to do with the engine itself as you know, and may need to be diagnosed by a experienced tech by getting it on a lift while running and listening/feeling all around for loose items like underbody shields or loose (or bent/touching chassis) exhaust components.
Harmonic vibrations in many cases (ruling out engine) may not be precisely identifiable at all, by anyone, aside from determining if it is within the engine, transmission or chassis.
Failing torque converters can cause it, trans oil pump, etc. Anything that operates in park while engine is on.
I've even felt a harmonic I swore was in engine bay, but was from the secondary fuel pump in tank, I felt it at my feet while sitting in the car and on my hand resting on center console, but not with my hand on fuel tank itself or in rear seat.
Another oddball on a x5 was vibration/harmonics only at idle in park and only while in drive, just off idle, then disappeared. Turned out the owner lightly backed into his garage door the week prior at exhaust tip and slightly put tension on rear muffler system hangers. Loosened up all the pipe and hanger brackets and smacked it around with a big rubber mallet, retightened everything and the annoying vibration and noise was gone.
Sometimes you gotta think outside the box I guess...

Last edited by gcguru; 09-05-2019 at 10:03 AM.
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