I have a '95 Integra, with almost 157K mi. on it. Just yesterday, my engine started vibrating. It does it when I idle, and when I accelerate. I can feel the vibration through the gas pedal, and I can hear it. It's louder than it used to be, and a deeper sound that I can almost feel more than hear. It gets worse up around 80 mph. and I can feel it in my seat, too. Any thoughts?