Rattle/chatter under load, not noticed while reving @ idle

[mab543]

So the last week or so I have been driving my M more since it's nice out, decided to get on the highway at which point a Honda SI tried to race me lol. So I played around a bit and noticed when i downshifted a loud knocking almost chattering sound on load (3 or 4th gear if I recall)... also the civic all but passed me. I actually thought for a week it was the Civic but today I took it out and realized it was me making the noise. So here's the deal, I got...

08 E93 M3 6mt
Owned since 72k and now has 92k
Cat less exhaust, all high flow
Evolve stage 2 tune
K&n intake
BE bearings done at 87k
Spark plugs done at 78k
CF drive shafts with green loctite on rear dif joint

To replicate the noise, It's only noticeable when I down shift a higher gear to a much lower gear and put load on the car to take off, or, I get low speed and simply put the car in a higher gear to accelerate hard. It's never noticeable when sitting idle and reving the engine. It continues through the RPM range under these conditions but goes away when i let off the gas and continue to drive normal.

I tried putting the GoPro under the hood and while you can hear the noise, it's concealed a bit on the video by what I would call other normal noises from the s65 engine.

So I've looked at exhaust, nothing appears loose or rattles more than normal. Didn't see any loose heat shields.

Check codes, had a few I didn't clear from last winter related to the 02 sensors and showed a thermostat error. I did notice my coolant was at the min, so I topped this off before test driving, no change. Guessing this caused the codes and the "increased emissions" message that would come and go over the winter but hasn't been on in a few months, it's a weekend car btw.

Checked a few of the spark plugs, didn't seem to bad But cleaned those few up.

Cleaned the MAF sensor and made sure I take was fastened tight


Based on my searches this could fall under a few different areas/items.

I was leaning towards a pulley tensioner but wasn't sure that would cause lose of power?

I considered the coolant thermostat but my heat works fine and the car seems to have good idle and temp reading on the cluster.

Thought maybe battery, checked the voltage with car off, reading under 12v which seems slightly odd in my experience.

Saw some threads mention vanos solenoids but know very little about these.

Lastly, thought maybe it's just a bad tank of gas. Thinking maybe some kind of pre-detonation but never experienced this in my life. I'm at half a tank and plan to fill up with ethanol free 93 which I hear we can get in PA. I usually just get Sunoco 93plus or whatever.


Just seeing if anyone else has been down this path.

Thanks!

[Scrippy]

Motor mounts still good?

[mab543]

Originally Posted by Scrippy

Motor mounts still good?

That's a good thought. I had them changed when the rod bearings were done not too long ago. I guess I'll have to check them.

[RedScytheM3]

Originally Posted by Scrippy

Motor mounts still good?

Originally Posted by mab543

That's a good thought. I had them changed when the rod bearings were done not too long ago. I guess I'll have to check them.

This is interesting, I've heard something similar before when I test drove an E92 prior to buying mine

The car was not fully warmed up when it happened. I took off out of the parking lot with a right hand turn and gave it ~60% throttle in 1st and second gears, shifting near 6 krpm. Over a range of 2 krpm before shifting into 2nd, I heard a rattle that sounded synchronized with the engine speed. It sounded similar to something being tossed around inside a chamber with a spinning fan. Kind of like running over an opened pine cone with a lawn mower. The car had 75,000 miles during the test and I honestly had no idea of the car's history. There we no codes, engine oil full, didn't see any leaks on visual inspection, no weird noises other wise. I did another pull later when the car was hot and head nothing. Sounded perfectly fine. I'll see if my car does something similar when I head into work in an hour. I'll have the phone recording a video on pull 1 and again on pull 2 when the car is hot.

[RedScytheM3]

Wasn't able to replicate it, but I've heard it. Maybe some VANOS clatter?

[atopa2002]

Check the exhaust gasket between headers and the Xpipe

I have a similar rattle with my newly installed xpipe, will be replacing my old gasket with this.
https://www.fcpeuro.com/products/bmw...js-11627830668

[Scrippy]

Originally Posted by RedScytheM3

This is interesting, I've heard something similar before when I test drove an E92 prior to buying mine

The car was not fully warmed up when it happened. I took off out of the parking lot with a right hand turn and gave it ~60% throttle in 1st and second gears, shifting near 6 krpm. Over a range of 2 krpm before shifting into 2nd, I heard a rattle that sounded synchronized with the engine speed. It sounded similar to something being tossed around inside a chamber with a spinning fan. Kind of like running over an opened pine cone with a lawn mower. The car had 75,000 miles during the test and I honestly had no idea of the car's history. There we no codes, engine oil full, didn't see any leaks on visual inspection, no weird noises other wise. I did another pull later when the car was hot and head nothing. Sounded perfectly fine. I'll see if my car does something similar when I head into work in an hour. I'll have the phone recording a video on pull 1 and again on pull 2 when the car is hot.

Maybe you have an exhaust manifold leak? Also I saw somebody bring up the collector to x pipe gasket which I agree could be a cause. Both ideas could sound like shit cold with an engine load applied until things heat up and expand and almost close the leaks. Maybe you can get an auto stethoscope and listen around all exhaust connection points....(manifolds, collectors and connection at end of x pipe where muffler system starts).

[Scrippy]

Idea-Record a video of a pull to 3rd along a wall or building or tunnel with your window down. This might increase the audible sounds you are hearing so we can hear and offer ideas. Don't let the wind hit the mic and drown out what we need to hear.