I agree with Dave. Once a plug is fouled throw it away. I went against my own advice and re used a set in my Dakota. Used them to plug the cylinders when going in with the engine. Had a slight miss at 2K and up. Put new plugs in and slight miss is gone. It was just a slight sputter but still there and bothering me. The open hood at night trick works real well. I have found several bad wires this way.