Vibration on downshift or when I let off of the gas.
I have a 2001 Ford Focus SE with 100,000 miles on it. I bought it used with 50,000 mile on it. As far as I know it has never had the timing belt changed. My car is making a vibration sound when I down shift or decelerate. What would be the most common cause for this? Also how would I know it was time to have the timing belt changed?