Big Evil ~
Hey! Did coolant flush, replaced thermostat, t-stat housing (used NEW OEM plastic housing, as crack independent mechanic said there are many cheap aluminum cast housings, and that they are actually less reliable), etc. And drove it a few cycles. CEL still on...
So I used Peake's "TUBE" and reset the CEL. Low and behold, it showed up again after 5 minutes of driving. Well, no big deal, as it needed a thermostat, anyway. But as opposed to throwing parts ($$$) at the car, I took it to the aforementioned shop (Euroquipe in St. Charles, IL - excellent). They read DME, and were able to test the O2 sensor independently (maybe easy, but beyond my knowledge) and they said there was absolutely no response at all - it was DEAD.
So, the sensor I could definitely do myself. I replaced that yesterday. I should mention that the "old" O2 sensor was indeed quite new, but it had broken pieces of ceramic-looking substance inside the sensor tip (viewable through the narrow slots). Evidence, perhaps, of why it was dead. ANYHOW, after replacing I reset the CEL, and viola! No more check engine light. And it starts with hardly any cranking, idles smoothly, and has better acceleration. The MPGs are already improved as well. Awesome!
Thanks again for your advice. I guess that after the most simple solution, it was the next (in this case). I'm sure I'll be on this site again, looking for advice, but hopefully not for a while!!!
Take care, and happy driving. Auf wiedersehen!