Unidentified Engine Noise

[Arsonism]

Hoped I would never have to post one of these threads, but here I am. (This is mostly a sanity check).

The Car:
08 M Coupe at 56,000. Service 2 completed at 46,000. Has had oil changes every 5-6,000 since my ownership at 39,000 (not intentional just got some freebies here and there).
AFE intake
RE Midpipe
RPI exhaust
Turner Power Pulleys

I have one oil analysis that I haven't sent in yet, and probably should but was holding off until my next oil change to send them both simultaneously.



The Noise:

Ever since I've purchased my coupe it has always seemed to have a "chain noise" almost like one you could hear rattling around on a bike but with a much more respective tone to it. It can mostly be heard at low speeds and on a colder engine (rolling out of a parking garage from work). I've noticed it occurs most when engaging the clutch as I'm coming to a stop. I've always figured it was something pertaining to the Vanos or the timing chain system, but assumed it was normal as nothing has gone wrong with the car and all systems seem to be go through daily driving.

Recently, I've started to have some bad coughs and some misfires at idle. Some of it can be attributed to me dirtying my injectors and possibly bad fuel, but as of late they've gotten worse. I wonder if the two issues have become related. Although whenever the fits occur it never triggers a CEL where before when I first had the car with no mods (no major drivetrain mods still) it triggered once under hard acceleration. The idle almost resembles the symptoms of a bad coil or injector like on the Z3 I had, but I wanted to double check with the board first to see if the noise could have something to do with it before going through and replacing a slew of stuff off hand.

Please ask questions if I've left something out and I'll be sure to answer it.

Thanks gents,

Skiddish

[Cyclops]

can you post a video of the car running?

you can also try using a mechanics-stethoscope and try to isolate where in the engine the "chain noise" is coming from. Harbor Freight sells them cheap. Just be careful using it as it really amplifies all sound, so don't bang it around.

[Arsonism]

Originally Posted by Cyclops

can you post a video of the car running?

you can also try using a mechanics-stethoscope and try to isolate where in the engine the "chain noise" is coming from. Harbor Freight sells them cheap. Just be careful using it as it really amplifies all sound, so don't bang it around.

Will definitely try one of those out. A little hard to pin point from the driver seat and I believe I have only noticed it while rolling. Will see if I can find something that better depicts the noise.


It does sound like a rattling chain, almost like you would hear on motorcycle if your chain was getting a little old. This is why it most concerns me. I'm coming from an M54 engine and this is definitely not something I came across working on that old gal.

Thanks again cyclops, I appreciate your response.