[snaeem155]

I have a plastic rattle/noise on idle which I cannot figure out.

It's almost sounds like a playing card in a bike wheel at low speed.

Tried seeing if its the blower system related but it doesn't make a difference if it's on or off.

I can't see anything that looks loose in the engine bay.

I also hear the noise when I turn the car off for a split second.

Any idea what it could be?

[iqraceworks]

Turbo wastegate rattle?

[opjose]

Can flap?

[snaeem155]

Its neither, the turbos don't have wg rattle and the exhaust flap rattle is only on startup and for a split second.

This is plastic sounding and sounds as though its coming from either behind the dash/engine bay towards the passenger side.

[snaeem155]

Just took the car out and I was overly looking out for the sound.

There was no noise when the car was cold, when the car warmed up after 10-15 mins of driving then the noise started.

[iqraceworks]

Originally Posted by snaeem155

Its neither, the turbos don't have wg rattle and the exhaust flap rattle is only on startup and for a split second.

This is plastic sounding and sounds as though its coming from either behind the dash/engine bay towards the passenger side.

Have you pulled off the cabin filter and looked at the fan? Could be something rubing on it?

[snaeem155]

I haven't yet, but that's the two areas I'm suspecting its coming from.

Either the cabin filter or the blower fan behind the glove box.

Just curious as to why it starts when the car is warmed up, on the outside due to the noisy nature of the N54 I can't hear it in the engine bay but can inside the car.

[opjose]

Btw can flap rattle occurs far more than "a split second" and may run for minutes.

It can also reoccur while driving as the car opens and closes the flap.

[snaeem155]

Its definitely not the rattle from the exhaust.

It happens at idle and is coming from the front of the car and most definitely definitely sounds plastic in nature.

[iqraceworks]

Originally Posted by snaeem155

Its definitely not the rattle from the exhaust.

It happens at idle and is coming from the front of the car and most definitely definitely sounds plastic in nature.

Not to sound like a jerk.....but good lord, how hard can it be to find where a noise is coming from? Listen for where it's coming from, and start removing parts until you find the issue. Compared to other complicated issues with the 335i/N54's...this has got to be one of the easiest things to diagnose, troubleshoot, and repair
..just follow the sound until you find it 😆

....just saying....

[Dave92N54]

Willing to bet $5 you're talking about this:

13907618652

[stewbets]

I'm with Dave here. Fuel tank vent valve under the intake manifold. The sound comes and goes.

[vaccaro79]

I'm having a very similar issue on a 2009 328i coupe stock (E92). Could it be the same fuel tank vent valve? multiple mechanics have not been able to reproduce the noise. The noise begins to become audible after warming up, it does not matter if the air is on or off, but only appears to make the noise in drive at idle.

This is a link to a video with the sound; in the video at the 14 second mark I put the car in reverse (still at idle), and the noise goes away.

https://www.dropbox.com/s/aes24vz7j9....mp4-.mp4?dl=0