some progress here. I got the car 8 days ago and though it idled rough (that problem still exists) in every other way it ran great. I did my normal catch-up maint the next day, including flushing the cooling system and hosing down the radiator. Right after that I got code 172 (o2 sensor lean) and lurching behavior, which lasted 3 days and then went away and all was well.
Then today I was swapping out the ECT and a pint or so of coolant spilled out, and right after that I got code 172 again, with the lurching, again. Seems that it must be a problem with some naked wires getting wet, though interestingly the o2 sensor wires' insulation is very much intact. Not really sure what to do, but anyway.....
