I’ve been chasing an engine miss, irregularly occurring for a couple months in my non-daily driver '76 XJ12C. I thought it might be fuel related as the worst engine running problem was difficult starting, fully warm engine, finally running, gave it throttle and it immediately died - so I checked fuel pump volume and it is fine. Fuel pressure is spot on too.
So I went back to ignition. I’ve had a Lumenition conversion kit installed on this car for many years and thought maybe the light beam trigger mechanism might need cleaning. I removed the distributor cap and was disappointed to get very little dirt film off both sides of the light trigger mechanism.
I replaced the coil and no more trouble. A few days ago, I picked up the old coil on the work bench and turned it over and felt the oil splash inside. Several times over the years, I have wiped oil residue off the top of the coil. I guess enough had boiled? out of the coil so now it wasn’t keeping cool inside.
Gave some thought to relocating the coil out of the V area of the engine to get it away from intense heat. But, coil only about $70 and the other one lasted about 10 years.