Hello All,

My Brick ('90 245, M47, 170K miles) has recently experienced a few hiccups. While nothing major, they're annoyances nonetheless. Can anyone offer advice?
1) Passenger side front (power) window just started making a "grunch" sound as it lowers all the way into the door. It still raises and lowers just fine, and doesn't appear to cause any damage. It only happens when the window goes all the way down into the door...if I stop at 9/10ths, no sound.
2) On warm starts, she'll crank, run for a second, then die. If I give her a little gas, she starts fine. However, when she starts cold (first thing in the morning), she starts and runs perfectly. Any ideas as to why? She runs like a champ otherwise.
3) I keep getting a 2-1-2 code (O2 sensor), but the guy I bought it from (a mechanic) just replaced it. I cleared it the other day, but after about 30 mins of driving, it came back on. Anything I can do short of replacing the sensor? Is it bad to leave it on like this? And if the CEL is on, does it mean that the ECU isn't reading the O2 sensor at all, or did it just detect a fault one time? I don't think anything's wrong with the sensor as I still get good mileage (30 MPG highway, 26 MPG mixed driving) and she doesn't run funny.

Thanks for any and all advice...
Matthew