How about heating up the threads, either with a torch, or try loosening it while it's hot from running?

Ed

> Date: Tue, 23 Nov 2010 21:41:01 -0500
> From: hhoffman@IP-SOLUTIONS.NET
> Subject: Rusted on O2 sensor
> To: vanagon@GERRY.VANAGON.COM
> 
> Hi All,
> 
> I'm trying to remove my o2 sensor but it's rusted in place. I've tried
> quite a bit of liquid wrench, along with a set of locking pliers and a
> hammer. No dice.
> 
> How do other people get the sensor off without destroying the cat?
> 
> Cheers,
> Harry