More info:
allowed it to idle until warmed up:
-disconnected the Idle Air Control Valve
result: engine stalls (IAC valve appears to be working, I think)
-turned on headlights or ventilator fan
result: engine stalls

On another forum someone mentioned a Electric Load Detector in the engine fuse box (I'll have to look into that and do a search through my electrical system; probably starting with all the grounds and battery connections)

No check engine light (so no codes).