Problem still unresolved. Anyone good at O2 sensor readings? The sensor is definitely working, and it maintains a mean average of .426v when at warm idle. It fluctuates slightly, but not much. But the engine does shake for a minute or so just before reaching operating temp, and the readings during this time shoot up to .8v and .9v. Once the shaking stops, it drops back down to .426v. At this point, the CEL lights up, but the idle is rock steady. Which tells me that the DME has compensated for something wrong. Bentley says it should be somewhere between .2v (lean) and .8v (rich) at idle, so being in the middle should be about right?
never mind, I found my answer. According to everything I've been reading, the voltage should fluctuate rapidly and across a wide spectrum, from .2v to .8v, and not remain steady. If the reading never goes over .6v, then the sensor is damaged or dead. And the fact that the CEL comes on and the idle smooths out means that the engine management system has gone into open loop and will run rich to compensate for the lack of O2 sensor input. So it seems I probably fouled the new sensor when I installed it