Cannot remove oxygen sensor
 

In my attempt to pass the emissions test, I need to replace my o2 sensor. I have tried and it will not budge! Any tips or tricks to remove this darn thing?

I have a 95 325is and I think it may be the original unit... ok sarcasm, but it does appear to be old and the car has 160k miles on it.

I am afraid I am going to strip it out or worse, break the cat converter.

Are you trying constant pressure? If so, try a sharp "jerk" to break the sensor loose. If you do tear the cat, it is not entirely impossible to weld in a threaded jam nut to hold a new sensor. You'd be surprised the things I've seen done to repair an O2 sensor port!

If the "quick jerk" method doesn't work...
My advice would be spray the exposed threads with WD40 or PB Blaster, gently heat with a propane or MAP gas torch, then try the "jerk" method again.

Just to make sure, you are using an O2 sensor socket, not just a combo wrench, yes?

-Nick

Thank you Nick. Yes, I bought the special tool for o2 sensors, but it's just not working.
It looked like it was going to work, but the tool either splits open or it slides up and dosent' bite to turn the bolt. I am going to try an open end wrench today and see if it will come off.

They have these located in a tough spot, on top of the converter. I had thought of dropping the exhaust system to do it?

Yea, I found that alot of the O2 sensor sockets out there are just too thin to do the job. Once you get the socket loaded, the gap for the wire expands, and it just slips off :(
If you can track down a Snap-on salesperson, they sell te best one I have found. You will actually shear off the sensor before the socket slips!

Let me know how it goes.
-Nick

Again, thank you for the reply. I didn't get to try it today. I cleaned the interior and went for a ride instead. I guess I will worry about the emissions test on Monday!

I am hoping I can get an open end wrench to it.

Liquid Wrench, PB Blaster etc. Run the engine to heat it. Basically may944's advice.

Well, it's coming off today one way or another! :)

I am going to soak it with wd40 when I get home and twist it until it turns out, or the whole exhaust system rips out.

Dont use WD40, get a product specifically designed to loosen stuck threads like PBBlaster etc...

Then apply, wait 5, run the engine 5, wait 30, apply, wait 5, attempt

CUt it
 

If you are replacing the sensor cut the wire and use a box wrench, the sensor is toast anyway.

Great news.... I got it off!!!! :)

Bad news... I cannot get the other one in. It appears the threads are messed up and the new one will not go in. I think I am going to have to take the exhaust down and have it re tapped.

I may just go ahead and buy a new cat converter anyway, just to be done with it all.

Where is the cheapest place to get a converter for a 95 325is?

I am just disgusted with all of this. I can't get the car titled or licensed until it passes emissions. This sucks.

Cats are very expensive.

Try chasing the threads with a tap.

I had a muffler shop retap and install it. How long before everything resets? I failed emissions the same day after installing the o2 sensor. Someone said it can take a day or 2 before it fixes the issues?