Just recently my 2000 Bonneville has started sputtering and cutting off at stop lights. I have also noticed at times that some of the gauges don't work. Several weeks ago I noticed that the radio stopped working but the car ran fine. After turning the car off and starting it again the radio worked. I also noticed weeks ago when going up a hill and accelerating I could hear a "clacking noise" that sounded like it was coming from underneath the car. Any ideas???