I've been chasing an intermittent ignition misfire for weeks and I'm completely stumped.
A timing light shows the coil lead has a consistent misfire. It also shows cylinder #2 misses far more often than the other three cylinders, and an adjustable spark tester confirms #2 will sometimes have a weak spark or no spark at all.
Everything is original.
So far I've replaced:
Spark plugs
Plug leads
Distributor cap
Rotor
Condenser
Ignition coil
I've also checked:
Points gap is set to spec and consistent on all four cam lobes.
Swapping plugs and leads doesn't move the fault from #2.
Distributor shaft has no play or wobble, and the cam lobes have no visible wear or taper.
Distributor feed-through terminal and internal wiring don't have any intermittent shorts.
Distributor cap terminals and rotor button show no signs of wear or damage and are not burnt or corroded.
I've also checked voltage at the coil which is within spec, and I've wiggled all ignition related wires and connectors with no change or difference.
What I can't understand is why it mainly affects one cylinder. If it were something like the coil, condenser or ballast resistor, I'd expect all four cylinders to be affected rather than predominantly #2.
Has anyone come across a points ignition system doing this before, or have any ideas what I should be checking next?