I was driving down I-75 yesterday(at about 80mph), when my car started to shake real bad. I started looking at simple stuff. Fuel delivery and filters, fine. Spark.....fine. I then started the car and started pullling plug wires. 2, 3, & 4 all made differences in the performance of the idle. But when I pulled the #1, nothing changed. The #1 plug was really black, while the rest looked fine. I even swapped plugs with another cylinder and the same results prevailed. What could be wrong I f I have fuel and spark and the cylinder isn't firing??