Ran O.K. before. What I did was we had installed the AC delco plugs, so I cleaded the black off of the tops of each plug, used scotch bright on the contact point where the coil assy rubs against the head when installed, and stretched out each spring inside the rubber boot, going from the coil assy to the plug. Worked a little better, so I then got some different Autolight plugs that didn't have the black coating on the tips and worked better.