94c4seminole

Here is my method for removing that pesky pre-catalytic, passenger side oxygen sensor on my corvette. I hope this will make it easier for anyone trying this for the first time, as I became really discouraged at first and left the sensor on for much longer than it should have been.

What I used:
Oxygen sensors
Rental Oxygen Sensor Wrench Set
Long ratchet extensions (or several small ones)
3/8'' ratchet (3/8" breaker bar to get it loose)
PB Blaster

First I go to Advance Auto Parts and rent this Oxygen Sensor Wrench Set and buy the oxygen sensors.

94c4seminole

When you have all the tools you need, put the front of the car up on jack stands or ramps and spray PB Blaster where the oxygen sensors bolt into the exhaust. This is especially helpful if the sensors have been on for a long time.

Once the exhaust is cool enough to work with, you can remove the Driver's side sensor easily from under the car with the long socket (middle one pictured above). Unplug the wiring first and make sure the connector is clean for the new one. There isn't a lot of room to ratchet loose the sensor so it takes a while, but it is straightforward. Make sure the wiring sits in a way that it does not touch the hot exhaust or engine block.

Now for the passenger side... It was really impossible for me to get a socket and ratchet on this one from underneath. Put the smallest socket from the set on the sensor while you are underneath the car with the ratchet hole facing the passenger door. You can see this in the second picture below, the manifold is above and you are looking down from right front of the car.

From above the car, take a ratchet or breaker bar (depending on how stuck the sensor is) with all the extensions on it and direct it down past the manifold into the socket. It is helpful to have extensions like mine that allow some play when they are halfway on. The have curved ends rather than square.

94c4seminole

Try to get it as straight up and down as possible and use the breaker bar if necessary to get it loose. Once it breaks free, you can keep turning the socket in small increments from above by lifting up the whole ratchet/extension/socket setup and placing it back down for another turn. Once it is loose enough, you can go back under the car and loosen the rest by hand.

94c4seminole

Tighten it on by hand as much as you can. Then do the rest from above just like you loosened it. I just get it snug, not too tight. You will be careful to do this too if it was a real struggle to remove in the first place! I'm no professional, but this sure helped me out. I learn more about this car every day.

Hope this helps, -Evan

P.s. for those who are more knowledgeable than me, please submit any ways to do this better!

charliet615

Good Article, Thanks for the Pictorial.....

don hall

Worthy of being a 'sticky'.... mod advised.

pkincy

I use the big O2 sensor socket with the relief so you don't pinch the wire. I do have several 12 inch extensions as well as a 24. So put the 24 on the socket and add a 12 inch. You can get the socket on the sensor from above although it is a bit tight. Make sure you get the socket all the way down on the sensor flats. Then untighten it about 1/2 turn. If you have used the OEM sensors with the graphite impregnated grease, that was enough for me to then get under the car and undo it from the bottom with my fingers. Don't use that socket to do more than 1/2 to 3/4 of a turn without unplugging the wire however. Then simply start the new sensor and I was able to get it within 1/2 a turn of the 30 ftlb torque spec from the bottom with my fingers. Than tighten from the top with the final 1/4 turn with a torque wrench on it and then back under to connect the wire. I have a lift so that underneath stuff is much easier.

The first time I installed a right side I neglected to torque it and what I thought was tight wasn't and I had enough of a leak that I failed my first smog test. After the retorque, no problem.

Now the hard part over their is replacing that cat and downpipe. Again driver side is easy but passenger side is not. Did that several years ago, when a blown engine totalled the passenger side cat.

Good Article. A lot of the secret is the more appropriate tools you own the better. I don't think the deep Sensor socket was much more than 6-7$ and I have used it a good number of times.

BTW, mine is a 93 which has a 1 wire sensor. I think the 94 has a 3 wire doesn't it? Less to get in the way of the deep socket with a 1 wire.

94c4seminole

Thanks for adding the torque spec. I have a hard time finding that stuff in the FSM. The '94 actually uses a 4 wire sensor. It does seem to pinch it on that deep socket, but it seems to end up alright. On the passenger side it doesn't get pinched at all using that short open socket. Thanks for adding in this info.

H P Bushrod

Done deal! When I replaced the O2 sensors on my '93, I did it from the bottom. They had the single wire.

antfarmer2

I did my 94 from the bottom too with the short socket to hard to get in and out and up and down to damn old.

don hall

Tell me about it.......

94c4seminole

Did you use a flex ratchet or something of the sort? I couldn't manage it from under there even with the short socket. I've got a lot to learn from you guys..

don hall

"you can use a box end wrench and just thread the wires through the box end."

Source: http://tech.corvettecentral.com/2007...oxygen-sensor/

94c4seminole

Oh I see. I think I tried that but the sensor is recessed on mine, so I had trouble with getting it seated. Well there are more ways than one! Whatever gets the job done.

antfarmer2

Nope just a regular wrachet with ext but my o2 socket was from Oriely's a little differant.

pkincy

Different sensors have their flats in different places. I agree some sensors have their flats high enough on the sensor to be easier to remove in each case. I find the Delco AFS21 to not have that characteristic. The only way a box end would get to my passenger side would be if it had two 45 degree angles built in....one 1/2 inch from the box end and the other 2-3 inches from that bend. Now had I not been able to get at it from the top I was ready to sacrifice a 7/8ths to the torch to make that extra tool.

Drew95

I must have moved O2 sensors left to right and right to left...seems like a hundred times hunting down things. That's Bosch, AC Delco, and NGK..they're all the same wrench.

You guys are FULL OF ****.

Never EVER used anything but a hand wrench, at the base.

I'm really not sure what anyone is supposed to learn from this.

pkincy

Gee, if we all were as smart as you think you are, none of us would ever need any extraneous information. I am not certain how you walk around and hold your head up given how much your brain must weigh.

Drew95

Actually, it was the opposite of being smart that lead to the advice, but whatever. Just offering .02... do what you want.

davewhtt

Don i miss the boat! Im about to do my 93 o2 sensors. Dave