O2 Sensor or AKA Pain in the ass...

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Jul 27, 2011
37° 52' 18" N / 122° 16' 18" W
Should stick with classic bimmer wrenching.....

Simple air filter replacement causes idle to crap out, now the frickin' O2 sensors...

What size bolt/screw head for cat converter cover on a '92?
10mm too big, 9mm too small, 3/8 too big, 11/32 too small.
Of course they are rusted.
They haven't been rounded...yet.

If they don't wrench off, they need to be cut off.
What is the best tool for this?
My first choice is an air grinder, but I figured somebody has already determined what is best.

Then, once the cover is removed, I get to battle the sensor nuts.

What's the dealer charge to do this?

Reminds me of the jag v12 coupe I had for less than 2 months.....required removal of exhaust man to change plugs.

Thanks in advance.
It is very inexpensive to have done at a shop. Don't remember for sure, but I think I was charged something like $25.
Good luck
I just finished replacing mine as well and boy were they FUBAR. They were rusted and not to mention TWO different sizes. I tried different sockets and I just ended up rounding the nuts. I got a larger pair of vice grips and used a torch to heat them up about 30 seconds. Voila, they came off no problem. Now I am chasing a PO125 code that popped up right after replacing them. Good luck.
That's funny, I gave up on bmw wrenching(newer) and sticking with cruiser wrenching. Can't get to anything on that damn bimmer.

Also a notable to mention is that I don't live in the rust belt and it took me longer to unplug the O2 sensors than taking them off.
I did this last summer, it was kind of a pain but here are some helpful hints.

1- spray down ahead of time with something like pb blaster
2- get these two items. when using them, make sure the socket is on square. Believe it or not, 3 of the 4 were pretty easy to remove.
3- when installing, use these so you never have to do this again http://www.amazon.com/gp/product/B0056L28DA

All of the above I used and it made it go much easier.

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