[Saall]

2011 335xi n55
Can anyone give me an idea of what this could be?
While in park I'll rev to 4k and let it come down. As it hits idle speed a rattle is heard. It happens 4/10 times. See video. Thanks

https://youtube.com/shorts/Oh1k6Fhl-iA

[ddogg35]

Sounds like a loose heat shield.

[anjuna]

Originally Posted by ddogg35

Sounds like a loose heat shield.

Agreed. When the engine comes back down to idle, there’s a few things that happen at zero speed.

1. Engine goes into idle mode (ignition hits PID loop to control RPM)
2. Exhaust flap may close depending on tune (most open above a certain RPM or throttle input, then close back at idle)
3. Additional low frequency shaking due to lower RPM - there’s actually a small dip after the revs fall (since fueling/ignition/TB was cut off/closed) and it must rapidly try to hit idle speed.

I’d be interested to see if having AirCon on/off has an impact on the noise.

Check yer heat shields, look at clearance of exhaust components (WHEN HOT!), and fix it if it bothers you enough.

I had this issue for a while because I’m a bonehead (though I’m lazier than I am a bonehead) and, like most of my problems in life, ignoring it long enough make the issue go away.

[Luis561]

Try grabbing your muffler tips and wiggle your exhaust around. Sometimes it moves around and starts hitting things. Stock exhaust?

[Saall]

Originally Posted by Luis561

Try grabbing your muffler tips and wiggle your exhaust around. Sometimes it moves around and starts hitting things. Stock exhaust?

Originally Posted by Luis561

Try grabbing your muffler tips and wiggle your exhaust around. Sometimes it moves around and starts hitting things. Stock exhaust?

Never do cheap exhaust work lmao. Turns out the guy used a double walled pipe when doing my secondary cat delete. The pipes rattle like crazy from the Inside. Like wtfffff lmao. Probably gonna drop it and re do it myself with my buddy's welder. Thanks for your input.