Severe Vibration in car

I was driving my 1999 Ford Expedition on the interstate when i notice a rattling noise from the front. Shortly after the rattling noise got worse and the whole car started vibrating. Any pressure on the gas made it worse. I ended up coasting off the nearest exit where i lost power steering coasting in the parking lot right off the exit. Now the car doesn't start unless the gas pedal is depressed and it makes a horrible rattling/grinding noise. Any idea what to look for thats broken/busted or what's wrong in general. Friends driving behind me said they smelled something burning when they were behind me.