Big Mystery Socket Head Bolt

[mummyjohn]

I heard a rattling underneath and found this large, socket head cap screw style bolt sitting by the muffler.  I point out the location in the second photo.

Does anyone know what this is?
And anything else that might be relevant about it/the situation?

[daantjie]

Don't think it's from the location where you found it.  It likely found it's way there from a location probably in the engine compartment.   Could be the bolt holding the engine mount to the chassis.   

[mummyjohn]

Oh I'm quite sure it's not from that spot, it just luckily lodged there and somehow never fell out on the road.  But by the size I figure it's something significant.

[Lance]

Starter motor

[SuitGuy]

Guessing by how oily that bolt is, I'd check your passenger-side motor mount, just below the turbo. It's a bolt that goes up into the cross-member through a 2-ish-inch circular hole below the rubber mount. If it is that bolt, I'd check/change your motor mounts while you're down there, save the headache of tearing it out later. It could always be the driver's side too.