Okay. Got back to it yesterday with a new set of plug wires. Immediately idled better, even with the original, cracked coil pack. Still got a misfire under load, but no codes. Replaced the coil pack with a higher-grade aftermarket. Seems to run well, though haven't had the chance to drive it a lot.
It has occurred to me that a weak plug wire might cause the computer to compensate with a stronger primary signal; hence the brighter test light, which had me ready to blame the PCM. Thanks for talking me out of it. It just never entered my mind that there could be two related and simultaneous problems.
Maybe I'll next figure out what's up with that occasional complete power loss on this car during hot weather. Everything dies (usually idling at a red light) and the outside temp on the panel reverts to compass direction, meaning, I guess, that the PCM has lost power. Always starts right up again and goes on. Probably AC and cooling fans triggering a systemic power loss of some sort.
Thank you both for your help and words of sympathy. Is a contribution in order?
Tuesday, May 9th, 2017 AT 5:35 PM