Engine Problems

[ghiagirl]

1977 Mustang with original 4,900 miles on it, new spark plugs, new PCV valve, new rotor cap. When parked, engine sounds great! About a 1/2 mile down the road and it can't maintain an idle, starts shaking runs terrible. Bring it home and park it, idle is all over the place. Cooled down and start it and sounds great again. Any ideas?

[kingcobraadamnelson]

make sure the spark plug nut cap pice what ever they are called make sure they are tight check the tune