Rattle

So my exhaust manifold has a crack in it. Along with that noise I've been hearing a metallic rattle around 1200-2500 rpms. It's not pinging from bad fuel or anything like that. I thought it was the heat shield on the manifold. I removed it and the rattle is still present. My cat is after market and does not have a heat shield. So it's not that. I also checked the drive belts. All are new and the pullies are in good shape. The noise is coming from the rear part of the engine, driver side I'm thinking. I'm gonna get it up on ramps tonight and see if I can locate the issue. In the meantime, any ideas what else it could be?

 

I have the same rattle. It’s been there for years. Usually starts when I’m just stopped at a light.

 

It's driving me mad lol

 

Ok, I found the source of the rattle! My upstream O2 sensor was loose! The pipe has a lot of rust and one of the nuts was missing and the other nut was loose. I tightened it up and found another nut. It’s “fixed” for now. But I’ll have to address it soon at a muffler shop. At least the rattle wasn’t something serious!