With experience, a good ignition scope can let you see issues with fuel mixture, full ignition circuit condition, deterioration of primary and secondary circuits and much more. It takes a bit of time and experience to learn to interpret all the subtle details in the pattern to catch some stuff. But basically everything that happens in the cylinder firing event is reflected in that pattern you see. You will see the coil charge before the event, the firing line as the spark gap is bridged, the burn across the gap of the plug during the spark and the oscillation of the remainder of the energy dissipating from the circuit after.
I have a great old Tektronix book that shows how to use their older scopes in industrial engines to identify worn internal components using transducers.
On modern DSO's, transducer and current probe use has become a very useful eye into many areas of vehicles that otherwise could require a huge amount of labor to see and diagnose. I have used many versions from old straight analog units to newer DSO's for diagnosis.
Oscilloscopes Rock.
Just what I needed was another toy for the toy box. LOL
