My Oxygen Sensor light came on 2 weeks ago. On older model 928s, the oxygen sensor was suppose to be replaced every 30,000 miles. I know the wire on the oxygen sensor was broken, found it when I replaced the radiator/transmission cooler . I figured it would be a good time to replace the sensor. I reset the oxygen sensor counter located on the passenger side between the door and passenger seat (this is what makes the clicking noise on early 928 models). I called DEVEK to order a new sensor and talked to Jim, who advised me on the replacement procedure. He said I probably would not need to remove or lower the Catalytic Converter on the '81 928.
The part arrived the next day and this weekend (1/8/00) I installed it. I started by raising the car (ramps/jack stands ), crawling underneath and spraying WD40 on the nuts that connect the catalytic converter to the exhaust manifolds, just in case I needed to lower the exhast pipe. I then traced the wire to a black plug in the floor about 2 feet from the passenger side edge. There was a small heat shield, held in place by two 8 mm bolts, that was in the way, so I removed it.
Next I removed the cover over the fuse panel, both the top and bottom covers and found the wire come through the floor. I found that the wire was had already been disconnected. The plug for the connector was there, covered with a piece of vacuum hose. I remove the vacuum hose and wiped off the connector. I then pushed the black plug out the bottom of the floor and followed it with the wire and connector.
Going back under the car I pulled the old wire out. I then used a 22 mm open ended wrench to loosen the oxygen sensor. Once loose, I unscrewed it the rest of the way with my hands (making sure that the exhaust was not hot). I then was able to remove the sensor. I didn't need to lower the catalytic converter.
I then got out the new sensor, making sure not to touch the end. I routed the wire through the hole in the large heat shield and up into the hole in the floor. I the screwed the sensor into the catalytic converter by hand, then tighting it with the wrench.
Inside the car, I gently pulled the new connector through the floor and connected it to the green wire. I pulled up the some of the slack wire.
Under the car I then pushed the plug (already attached to the new sensor) into the hole. I used a small metal punch (1/16 " diameter) to push the lip over the edge of the hole. I then replaced the small heat shield.
The whole process took less then 2 hours, the cost of the oxygen sensor was around $65.
Copyright 2000, George A Suennen