89 cad sedandeville 4.5. Just had wires, dist cap, coil replaced. Cap had center top burned out. Still misses except when hard on the gas. When running about 30 to 40 mph and coasting seams as if the ignition switch is going off and on and cause some minor back fire. Shop does not seem to know the problem. New here and I need help bad. My wife loves this car and wants it fixed.