i have 1 sensor on my 94. i rented the o2 sensor removal tools from local auto parts store but even the smallest socket (7/8") was too big and not getting a good fit on my sensor. i dont have a 21mm open ended wrench (weird size). is that the size socket i need to remove this? while laying on my back i wasnt able to get enough torque with the vice-grip to get it loose either.

 

Any oxygen sensors I have come across need a 22mm wrench.

 

Yep, I've always used a 22mm open end wrench as well. No need for the special socket.

-Rod