What a PITA!! I have soaked this thing with PB, even went and bought the O2 sensor wrench (piece of crap). This thing is stuck in there like it is welded. I think I am going to give in and just remove the manifold. All the O2 sensor wrench did for me was spread open enough to spin on the sensor and round off the corners. I don't have a torch to heat up the manifold with except the little propane canister but I can't get it up in there. Any suggestions?

 

Sensor is shot? Cut off the wire flush with the top of the sensor so you can use a 13/16 (I think) six point deep socket to get a good grip on it. Use 1/2" drive tools to reduce flexing. Run the engine for a few minutes to heat up the manifold.
Sometimes the sensors are REALLY stuck and you just have to give it your all. Only remove the manifold if you're going to get totally medieval on it. Once off the car the manifold is a lot harder to restrain and get adequate torque on the sensor. Good luck.

 

Thanks Iaugapfel, I had already tried cutting the wire and driving a six point 7/8 socket on it but could not budge it. Tried from both the top and bottom and could not get enough uhmf to break it loose. Run the engine to get it hot, sprayed it with PB several times. I had the manifold off in 20 minutes. Laid it on the garage floor and stood on it while someone else did a drop kick on the breaker bar and the sucker came loose. It was cross threaded in the hole. Now I have to get a thread chaser and fix that. We just did head gaskets a few months back so I figured the manifold bolts would still be pretty easy to get out.

 

Try some PB Blast to loosen up the connection -- let it sit overnight, blast again in the morning. Then before you try to get it out, be sure to wipe all that liquid off so you don't slip with your socket.

 

Thanks for the tip Liberty but I tried that, ended up removing the exhaust manifold and found out that it had been cross threaded in the hole. Finally got it removed, cleaned up the threads and coated it real good with anti seize (just the threads) and put it all back together.