94 525i o2 sensor code help!

[noE30]

Whats the likely hood of replacing an o2 sensor only to have it fault out 1 week later?
3 weeks ago the check engine light came on and it was 1221 for the o2 sensor, I drove the car for around a week and half or so before changing the sensor. During this time the car drove perfectly fine.
The day before i changed the sensor the car started to run in "limp mode" so to speak, it would only rev to around 2k or so and was extremely sluggish. The next day after changing the o2 sensor the car ran shitty still until I disconnected the batter for a minute or so. After that the car drove great with no CEL until yesterday, it has now been a week or so since i replaced the sensor. The check engine light is on and giving the same 1221 code as before but, the car runs totally fine. If I reset the light it comes back on in a mile or so.

Could it be that the new o2 sensor is faulty? I find it hard to believe because the car ran great for a week, could the car really cause the sensor to go bad that fast? Or is there something else that i should look into?

I'm supposed to be driving cross country this coming wednesday, I desperately need to get this figured out.

Thanks so much

[AndrewBird]

It's possible that the new o2 sensor is faulty, but I'd bet something else is wrong. A vacuum leak or or a bad MAF can also throw an o2 code. I would start by looking for vacuum leaks.

[noE30]

I see. Might have to try get a smoke test done on Monday

[AndrewBird]

One common place for leaks is the intake boot. Cracks form inside the "bellows" of the boot. Pull it out and take a look at it while flexing it around. A crack/tear will be very apparent.

The hose and plastic clip under the intake manifold connecting to the ICV is another place to look. The clip that holds the plastic part into the manifold can break and then this hose won't seal properly.

[noE30]

the car is now alternating between codes 1222 and 1221. Its never both at the same time. Just one or the other.

[noE30]

Smoke test checked out fine along with a test of the fuel system, nothing out of the ordinary was found. No leaks or drainage in the fuel system or vac leaks.
Mechanic replaced the MAF sensor and the coolant temp sensor (the one for the dme) and the car runs the same. Bogs down excessively once it is warmed up, no power at all, very sluggish. Mechanic thinks it could be the cats..

[Dj Buttchug]

Op OHM out all your ignition coils. .4 to .8 is acceptable.

[LuxuryStatham]

Smoke test checked out fine along with a test of the fuel system, nothing out of the ordinary was found. No leaks or drainage in the fuel system or vac leaks.
Mechanic replaced the MAF sensor and the coolant temp sensor (the one for the dme) and the car runs the same. Bogs down excessively once it is warmed up, no power at all, very sluggish. Mechanic thinks it could be the cats..

did you ever figure out what the problem was?