MOTORCRAFT DURA-Spark II Electronic Ignition System: Testing: Notes
CAUTION:
When checking the secondary voltage, do not remove the No. 1 or 3 spark plug wires while the engine is running.
Perform the following tests using an oscilloscope which has inductive type clamps. Always follow the scope manufacturer's instructions. Also use suitable grounding probes and insulated pliers where necessary.
NOTE:
On vehicles with catalytic converters, do not run the engine for more than 30 seconds with a spark plug wire removed.