I HAVE A 318 IN MY 65 PLYMOUTH SATELLITE. LATELY IT STARTED POPPING WHILE IDLING. I CHECKED TO SEE WHICH CYLINDER WASN'T FIRING AND FOUND OUT THAT #8 IS NOT. I PUT A NEW PLUG AND IT IS STILL NOT FIRING ON THAT CYLINDER. ANYBODY HAS AN IDEA WHY IT IS NOT FIRING? IT JUST STARTED DOPING IT YESTERDAY. THANKS FOR ANY HELP.