Ignition as perpetrator? Or Ignition as victim of intermittent power feed from tired Ignition Switch?
You must be registered for see images attach
BTW, nice scope sleuthing! If you have your scope handy, possibly channel 1 on the power in and
channel 2 on those reference pulses? And if both go missing simultaneously, then you can
pursue the flaky ignition switch theory with confidence. And if this section of power is OK, then
I'd check the PCM power as well. Sometimes it isn't the parts or even the wiring, but just the
lowly ignition switch with countless mechanical cycles visited upon it.
FWIW I've included a couple wiring diagram pages for your viewing pleasure. Didn't want to wallpaper
this thread, but if you have downloaded a TBI-era FSM for the electrical & emissions stuff there's
a lot of good info in there.
Best of luck. Rootin' for ya!
Just some troubleshooting food for thought.