I've developed an intermittent electrical misfire. Only happens when it's hot, and appears to get worse the warmer the car is. Symptoms are momentary loss of spark (tach needle drops, then bounces back up).
I've tried an spare ignition module and it's not that. I've got a spare cap and rotor to try, but I haven't got a spare coil to try. They're not cheap, so I don't want to buy one unless I've been able to prove that the current one is the problem.
It's the stock GM, in cap coil - anyone got a spare that I could borrow for a while for testing?