E90 rattle on start and when accelerating or revving engine

[wazefan]

I just bought an E90 328i, and about a week ago I started to notice it has a metallic rattling sound. Its a pretty well maintained car, but I don't think it's been driven frequently in recent years, and its coming up with some problems now that I'm commuting and taking it on road trips. The only things I've done to it in my one month ownership have been spark plugs and replacing the belt tensioner pulley which was going out. The rattling isn't constant and is especially loud when starting the car and when accelerating or when revving in neutral. It seems to be coming from the front of the car near engine, but I'm not 100% sure, and while driving it can only be heard with the windows down. I'm worried it could be the timing chain, since it has a bit over 200k miles, and that service still hasn't been done on it. Any ideas?

[zellamay]

I'd first look at all those metal shields, to see if one is touching anything. Timing chain is more of a grinding sound, with some rattling in there too. Timing chain noise will very clearly be coming from the front of the engine. You can post a video for others to listen to.

[wazefan]

Thanks for getting back to me! Yeah, my most recent idea is heat shield rattle or something like that. I also sent the video to my friend who's more experienced who said it sounds like exhaust rattle or something similar like a metal shielding.

https://youtube.com/shorts/pTeqrJJkaTQ?feature=share

[marvinstockman]

Have car lifted, and run car while on lift.

[wazefan]

Would love to, but don't have access to one. Maybe I'll try to rent a shop space for a few hours or stop being cheap and just take it to a repair shop to diagnose (though that does ruin some of the fun)

[drewusmaximus]

Definitely sounds like a chain rattle. Sounds like one of the guides broke and when you accelerate, the chain speeds up and is hitting a broken guide. I hope that's not the case or it's not a loose oil pump, but that occurs on the 8 cylinder I believe.