Oxygen Sensor woes - OBDII codes - now what?

[dpski]

OK, here's the gory details, 1997 850 non-turbo, 122k miles. Runs good.

About a year ago CEL came on, pulled the OBDII codes; P0133, P0136, & P0140

P0133 = O2 Circuit Slow Response (Bank 1, Sensor 1)
P0136 = O2 Circuit (Bank 1, Sensor 2)
P0140 = O2 Circuit No Activity Detected (Bank 1, Sensor 2)

About that time I bought the front & rear O2's from FCPGroton before Bosch jacked up their prices 40%. I figured with over 100k on the car they were due. Well the car has been running good, no change in mpg 24~26mpg so I never bothered to change them.

For whatever reason I got motivated this past weekend after changing the oil and tackled the replacement per the procedures on Bay13.

Before I replaced them I pulled the codes;
P0133 = O2 Circuit Slow Response (Bank 1, Sensor 1)
P0138 = O2 Circuit High Voltage (Bank 1, Sensor 2)

Replacement went o.k., little trouble removing the rear O2 senser.

Cleared the codes and was happy as a clam. Until the following day, when the CEL came on again. This time pulled the following codes;
P0133 = O2 Circuit Slow Response (Bank 1, Sensor 1)
P0140 = O2 Circuit No Activity Detected (Bank 1, Sensor 2)

Car runs fine, same as before. I'll admit to not checking the voltages on any of these, not really sure where/how to, however now I'm thoroughly confused.

Any ideas?

Thanks,

DP

[Guest]

Come on, say it with me, "If it ain't broke, don't...". Seriously though, my mileage has been horrible so I really need to purchase (40% price increase since you bought them, ouch!) and change out the O2 sensors and maybe tap that MAF a few times with a screw driver to knock to crud off as suggested by someone else in another thread a while ago. Well, and maybe replace the black accordian hose from the ETM to the Air Filter while I'm at it. Don't really know what to say other than I'll be keeping my eye on this thread for additonal O2 sensor tips dos and don'ts and things to watch out for.

[dpski]

OK, so I fixed this problem, without lifting a wrench. Here's the sequence;

After the CEL came back on the day after I changed the Oxygen sensors I retrieved and cleared the codes again.

I then drove the car back and forth to work the next day.

The next day I drove the car again, and again, and again. I've been driving the car for well over a week now, 400+ miles, and the CEL has not come back on. Maybe the computer just needed a drive reset period or something or I just got lucky, keepiin' my fingers crossed.

Anyhow the car seems to have better performance after a cold start and during warm up. It also seems to have better roll-on acceleration.