I have a bad o2 sensor, the upstream on the passenger side, any tips to getting that out, i am having trouble with the plug. How is the best way to separate the plug. it is on an 03 disco.

 

Not sure what tools you're using but a few people go for the lambda wrench to get it out.

 

The electrical plug should just separate, if the 02 sensor is stuck, try to remove it when it is warm.

 

Just did mine.
Remove the plug from the mounting point.
Then, use a small flathead screw driver in the seam between the two plugs and twist to release. Hard to get both hands in there to securely pull them apart.

Soaking the O2 sensor with penetrating oil made for a very easy removal from the Cat.

 

I soaked in rustblaster over night and will try to loosen it this morning, the plug is hard, thanks for the screw driver tip. Last thing to fix on the disco.......this week anyway.

 

I wish I had more advice. I changed mine at around 135k and they came right out. Most auto supply houses will rent you the special o2 socket. Otherwise, heat is good. Run the truck get the exhaust pipe hot (be carful protect any exposed skin) then try wrenching it off. It should come off with no issues.

Remember to apply copper anti seize to the threads of the new o2 sensor. Do not get the anti seize on the sensor head.

 

You should replace both front 02's to keep both cylinders balance with the proper air/fuel ratio.

 

I am replacing the other one next payday. After head gaskets, maf, and o2 sensor i am flat broke.

 

Empty yo' wallet! This is Rover repair!