Install the new O2 sensors into the new down pipe bungs, save tge plug they provide and take the O2 sensor out of the exhaust manifold later, install the plug into that threaded hole.

 

thanks don - yeah, i definitely don't want to make more work for myself and will use the existing studs & old nuts if the new ones don't fit the old studs. The img prob doesn't match the link cuz you can't see the offset part where you attach your 3/8 wrench, but it is the same tool... i was going to get the harbor freight regular socket but after reading several reviews that it tends to flex and pop off due to inferior quality, i decided to go with this style. I did check fit on the new O2 sensors and it fits. I was starting to wonder if there was more than one size for an O2 sensor but I don't think so. I will have to go back later and try to get another look at it with the camera to see what might be holding it from sliding all the way down. The oak pollen has been horrendous and no rain - last week i made the mistake of trying to clean some off the car and paid the price for a few days.

Old Blue - if i understand your suggestion, are you saying to just install the upstream sensor on the new cat and until i can get the old O2 out on the manifold, just cut the wire off the end of it?

 

Yup, leave the new sensor in the pipe, not the manifold

 

In your pic, you can see the flats of the socket aren't aligned with the flats on the sensor.

The area with the square hole for the ratchet extension might be contacting some portion of the manifold, preventing it from dropping in all the way.

But if you're going to cut the wire, you can use a regular socket.

 

A small problem with leaving it in is that there is a through hole on O2 sensors. The way they work is comparing fresh air to the exhaust fumes. May be OK.
I would take the down pipe off then probably get a wrench in there. Maybe move the bung bolt to the manifold.

 

My suggestion precisely, just to wait until he can work in his car in warm temperatures

 

I actually had tried various positions with the socket and when turned towards the rear of the car the extension is definitely clear of contact so not sure what is in the way. I also would push it down as far as i could and slowly turn it so it would line up with the nut. This is where one of those snake cameras would be helpful

 

Cut the wires off and use a 7/8 deep six point socket with an extension and long breaker bar , that looks clean enough you should be able to remove it easily


The crow foot tool just takes up too much room . Alternatively you can remove the exhaust manifold

 

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O2 sensors can typically be categorized as either a narrow band or wide band sensor. A sensing element sits inside the sensor, encased in a steel housing. Oxygen molecules from the exhaust gas pass through tiny slots or holes in the sensor’s steel shell to reach the sensing element or nernst cell. On the other side of the nernst cell, oxygen from the air outside the exhaust travels down the O2 sensor and makes contact. The difference in the amount of oxygen between that present in the outside air, and that present in the exhaust promotes the flow of oxygen ions and produces voltage.

https://www.delphiautoparts.com/usa/...-oxygen-sensor

 

For that particular sensor I would use the other type of socket or, do as Oldblue says cut the wires.