In December, my '84 GL overheated badly as I was = running up I95 through Massachusetts. The water pump had seized. I had it towed = back to Maine. For numerous reasons, I didn't finish the water pump job until = today. Everything seems fine when I start it, runs nice and smooth, warms up = normally. As it warms however, it begins to run worse, black smoke out the = exhaust. I think something (O2 sensor?) that's supposed to tell it to cut back on = fuel as it warms up isn't working. Maybe something I forgot to reconnect? Or disconnected accidentally? Something the overheating damaged? What = should I look for? Where is the O2 sensor anyway?