I have an 87 eltigre 6000, 530 that only runs on one cylinder. when I pull the plug wire off the plug it arcs and fires the cylinder but when it is on it won't run the cylinder. Also when it is on it fires randomly, like every 8 seconds. The other one seems fine. When I switched the wires it did the same thing but opposite. I have replaced all the plugs, wires, caps, coil, cdi. Did I replace with the wrong part or what is the deal?