Ok, so here's the story. I get in the car and drop the top down, I go to start it, and right when the engine starts, I hear a clang, or bang of some sort, and all of a sudden the whole car vibrates in tune of the engine, it still runs though. I think that the balancing weight on the driveshaft might've flown off, but I want to be sure. I told my mom not to drive it until we figure out what's wrong. Any suggestions on what to do, or where to take it to get checked?