More of a psa, 2 years ago I replaced the o2 sensors on my e36 m3 to help pass smog. Shortly thereafter I failed smog.
Crap.
So I ran a can of sea foam through the motor via a vacuum line and the exhaust never seemed to clear up. I figured I had killed my cats. So I grabbed a set of cats from a buddy who just swapped an ls into his m3. I used my awesome cordless impact to bust off my exhaust and after installing his, I had a check engine light come on.
Crap again.
codes said I lost both o2 sensors which I had left installed in the car for the cat swap and which are pretty close to the joints I took apart.
That's when I learned that the hammering action of the impact wreaks havoc on delicate o2 sensors.
So I shelled out another wad of cash and bought my 3rd and 4th brand new bosch o2 sensor in as many weeks.
Moral of the story: gently remove your o2 sensors before beating away on the exhaust - especially with an impact.
