I have a 1992 mercury cougar when I press on the gas the engine vibrates when I reach 20-25 and 40-55 all other speeds it just runs rough. When I am in neutral and I give it gas the car does not shake at all. What is wrong? Is the engine coming lose from the frame? If I keep driving it in this condition what will happen? I bought the car for 700$ mileage is now 147K I cannot afford major repairs on this car mainly because it has other problem and will never pass inspection again. Is it safe or will it blow up. When I do drive it I try to stay away from the major vibration speeds. Is it safe to continue?
Start with new spark plugs and air filter. Results?
Then, change the distributor cap and rotor. Click on these instructions: http://www.autozone.com/servlet/UiBroker?ForwardPage=az/cds/en_us/0900823d/80/14/cd/c5/0900823d8014cdc5.jsp