Rattling or Vibrating Exhausts
Rattling and vibrating noises under the car could be caused by a misaligned or broken exhaust system touching the under body of the car. This should be attended to immediately, as this may cause your exhaust system to prematurely fail.
If your car seems sluggish, has lost power or is using more fuel, it may have a blocked Catalytic Convertor. This should be checked immediately as other problems may occur.