Rod knock or something else?

[bmwforlife335i]

Hello guys, wanted to see if anyone could help with an advise if its not a rod knock to what it can be?

Here is the link to the video, the car is fully warmed up and idling, nothing can be heard from inside, and very faint sound when standing outside, however, from under the car more toward the right side (passenger) is where it is the loudest:

It is happening only on Idle, the slight RMP increase make it disappeared, here is the video of slight revs of the engine

The story on the car, it is 2014 M5 competition package 100k on the odometer, but it is all misleading, as the engine got locked up on it (busted oil pan) and I finally got around replacing the engine from a wrecked donor 2013 M5 with ~ 60k miles on the clock. So, the engine is with 60K paired with original transmission 100k. Prior the swap, I ran the donor engine, however, due to the fact that it had full straight pipes and free flow intake, it wasn't possible to hear such noises, at least I didn't hear them.
Now I am wonder, if I end up putting the engine that is on the way out, or I it is not the rod knock. At the same time, I drove the car already for around 800 miles, with no apparent changes in the noise level or its intensity. I sure hope perhaps it is the injector related problem, or maybe even flywheel noise, or whatever else it can be.
I would think if it was indeed the rod knock, it would not go away with the very slight RPM increase, car idles perfectly fine, in fact no any issues at all.

[Alrock31]

It doesn’t sound like a rod knock.

[M5Rick]

It's that 'sewing machine' noise I've heard before, does it go away when you put DCT in gear..

[bmwforlife335i]

No being in gear vs neutral or parking makes no difference on the noise. The only thing that makes it go away a very slight increase in the rpm. I think it idles around 500-600, so going up to like 900 makes it disappear

[M5Rick]

Like Alrock31 says it's not rod knock or it would be pronounced, I don't think it's a big problem if it disappears above tick over, if you can increase the tick over to some more see what that does. A/c on and off does it still do it?

[bmwforlife335i]

Originally Posted by M5Rick

Like Alrock31 says it's not rod knock or it would be pronounced, I don't think it's a big problem if it disappears above tick over, if you can increase the tick over to some more see what that does. A/c on and off does it still do it?

Sorry took a while, good point was to check with the ac being off, however, ac didn’t seem to make the difference.

[bmwforlife335i]

Originally Posted by M5Rick

Not sure, it's as if a flap is opening somewhere letting out excess gasses from the manifold at tick over hence the extra whoosh of gas noise.

Crazy thing that I could swear at one point after I came home from a trip and doing a couple of small revs, leaving it running the noise had disappeared, and it was running nice clean, makes me think definitely not the rod, but I could never do it again..
I ordered a blackstone oil analysis container, will sample to see what is going on with the oil to give me a peace of mind

Another test I could do, is while it’s running try to have each cylinder disabled(injector or spark plug wire) to see if the noise disappears on any of them. It’s going to be a pain though to get it done, plus it’s so already hot outside by the time I get to the last cylinder will fry my hands

[M5Rick]

Originally Posted by bmwforlife335i

Crazy thing that I could swear at one point after I came home from a trip and doing a couple of small revs, leaving it running the noise had disappeared, and it was running nice clean, makes me think definitely not the rod, but I could never do it again..
I ordered a blackstone oil analysis container, will sample to see what is going on with the oil to give me a peace of mind

Another test I could do, is while it’s running try to have each cylinder disabled(injector or spark plug wire) to see if the noise disappears on any of them. It’s going to be a pain though to get it done, plus it’s so already hot outside by the time I get to the last cylinder will fry my hands

You can do a blackstone or just inspect the old oil filter between the folds at oil change time to check if all is well.