sorry guys, but it's not chevy or truck related, thus the garage is off limits. but i need help. ok, so i'm borrowing this volvo right now. it's a late 80's wagon, 4cyl of some size, and a manual tranny, rear wheel drive. now, i'm kind of an idiot, and my muffler detatched from the exhaust pipe not too long ago and i didn't fix it right away. now, my tools got stolen, so i can't fix it. it's been backfiring when i let off the fuel while in gear because of it. anyway, point is that this afternoon it started doing this crazy popping from under the floor boards near the driver's and passenger's feet (therefore right next to the tranny). this mostly only happens when starting in first gear or when you first fire up the engine (tranny in neutral). anyone got any ideas what this might be?