i have a 97 mustang gt and its runnin kinda rough. at idle it will sit there and run fine for a minute and it start running rough and shakin the hole car then it will go back to runnin smooth for a min...i have already changed the spark plugs thinking that was the problem but it didn't help any...anybody got any suggestions

 

do a complete tune up wires rotor cap fuel filter. check air filter. pvc