I have a 1993 ford mustang with the 2.3 in it. The back end has been vibrating between 40-70 mph. I have tried everything and am at a loss of what could be causing it. Also the check engine light has been comming on and off frequently and the car is running very poorly after idiling for a while. I have only had the car for a month or two so am not very familiar with it just yet. Does any one have any suggestions??