Okay, most of you guys know my car, '92 325i/M50 (OBD I). I'll try and make this short . . engine threw a CEL about 10 days ago, fault code 1221, which is the O2 sensor. While waiting for the sensor to come in the mail, the car drove crappy- hesitation under acceleration, loss of power, rough idle, greyish exhaust smoke, and in once instance, the car died.
Once I installed the new O2 sensor, the CEL remained lit, and goes on and off intermittently. The car ran rough for a day or two, but now it's stable and idles well. No more loss of power. There's still some grey smoke, but not often. The car is now responsive but the CEL is still on. I checked the MAF, the ICV, and the throttle position sensor, and they're all working fine. The O2 heater and relay tested fine. I've read that it takes a couple of cycles before the CEL shuts off and the fault is cleared, but this should have happened by now. The only thing I can think of is if the new sensor is defective, or maybe I fouled the sensor when I installed it, but I was very careful about that. Anyone have any ideas? I'm at my wit's end here