^^THIS^^ NEVER pull plug wires off electronic ignition of any kind!!! You can "kill" the electronics. If you want to see whether one cylinder is not firing, you can such as this:
Loosen the dist boots and rig a thin grounding probe with a wire to ground. Using insulated pliers (plastic) pull the wire somewhat out of the dist tower and then slip the ground probe down in so the spark has a path to ground
The "open" plug wire you pulled is sort of like lightning. It causes tremendous open circuit high voltage which feeds back from the coil back into the box.
