Oxy Sensor Wiring Question - '80 SC Targa

[toddetch]

Hello Pelicans,

I'm still trying to solve my problem with running rough after the engine heats up. There's a long backstory but the summary is that when I replaced my fuel accumulator to fix my hot start problem, I found a disconnected wire, which another Pelican suggested was an aftermarket Weatherpak connector to the oxy sensor. Sure enough, that was correct. It was past time to replace the oxy sensor anyway so I replaced it and plugged it back in. Now, I'm not sure if it was coincidental or not, but after those two repairs (accumulator and oxy sensor) it started running rough once it was good and warm. My mechanic has been over it, checked fuel pressures, etc. One idea I had was that maybe this connector was not working so well, especially once it got warm so we decided it would be worthwhile for me to remove the connector and splice the wire.

Here is a pic of the current situation, once I got access to it and removed some electrical tape around the wire above the Weatherpak connector:



The white arrow points to the connector. The blue arrow points to a solder joint between the connector and I believe the original wire. The red arrow is really my question (sorry it's a little difficult to see). It looks like the original wire had an inside wire sheathed in green, then maybe another wire outside that, also sheathed in green. Was this grounding maybe? Was it just copper sheathing to reduce electrical interference? Any suggestions on what to do? If it is grounding I guess I could strip back a bit more of the sheathing and find a way to ground it (just to the chassis?). If it was just sheathing to reduce interference, I guess I could just cover the whole thing with some heat shrink to clean it up.

Thanks in advance for any advice!

[tirwin]

Yep, it’s a 2-wire system. There are 2 separate pins in the 12-pin connector. The outer is a both shield wire & ground. The inner is very low voltage (1V or less depending on AFR) so it’s susceptible to interference. The other end of the harness is the Bosch box under the passenger seat.

[toddetch]

Originally Posted by tirwin

Yep, it’s a 2-wire system. There are 2 separate pins in the 12-pin connector. The outer is a both shield wire & ground. The inner is very low voltage (1V or less depending on AFR) so it’s susceptible to interference. The other end of the harness is the Bosch box under the passenger seat.

Thanks @tirwin. So does that mean that my go forward path should just be to clean it up and cover heat shrink? Do I need to actually somehow connect that ground wire to something else? Or, if I can find some kind of shielding wrap should I try to join it to the remaining shielding?

[tirwin]

Pic from the Bentley showing inner and outer wire. Follow the wires on pins 2 and 4.

[tirwin]

Edit: NOPE. NOPE. NOPE. I was wrong. Doesn’t appear you need the outer wire connected. I just found Louie85’s old thread and he only uses the center wire. I did this a long time ago so my memory was fuzzy.

Pelican Louie85 used to make replacement O2 sensor connectors. I don’t know if he still does. I think I read recently where someone else is making them. Maybe he isn’t anymore? I would try to get one of those. They’re inexpensive and it’s a great fix.

Link: O2 Sensor connector

I would probably cut that inner wire and re-solder it with a piece of shrink tube on the inner part and then put another piece of shrink tube on the outer part of the whole thing.

[pmax]

Originally Posted by toddetch

Hello Pelicans,

I'm still trying to solve my problem with running rough after the engine heats up. There's a long backstory but the summary is that when I replaced my fuel accumulator to fix my hot start problem, I found a disconnected wire, which another Pelican suggested was an aftermarket Weatherpak connector to the oxy sensor. Sure enough, that was correct. It was past time to replace the oxy sensor anyway so I replaced it and plugged it back in. Now, I'm not sure if it was coincidental or not, but after those two repairs (accumulator and oxy sensor) it started running rough once it was good and warm. My mechanic has been over it, checked fuel pressures, etc. One idea I had was that maybe this connector was not working so well, especially once it got warm so we decided it would be worthwhile for me to remove the connector and splice the wire.

Sounds like the O2 sensor is working when the engine runs different when it's plugged in. It could be running rich when unplugged which can mask other issues (leaks) you have. Another thing occurred to me given what you said in your other thread... check your throttle switch. It's supposed to kick in on acceleration and make the system go open loop. If that's not happening, it would explain the hesitation.

[gazzerr]

I seem to remember in a thread recently that someone had this rough running issue and it was solved by properly grounding that outer wire sheath (your red arrow) that goes to the 4 NCA (no color available?) pin on the OXS control unit. I've never seen a picture of how to properly do this. Hopefully someone will chime in on how to do it ...

[tirwin]

Originally Posted by gazzerr

I seem to remember in a thread recently that someone had this rough running issue and it was solved by properly grounding that outer wire sheath (your red arrow) that goes to the 4 NCA (no color available?) pin on the OXS control unit. I've never seen a picture of how to properly do this. Hopefully someone will chime in on how to do it ...

That doesn’t make sense to me. If the O2 sensor is disconnected the system goes into open loop so the FV duty cycle is fixed at 50%. If it made that much of a difference, then there are probably other issues.

In Louie85’s thread he stated that the outer sheath was not connected to anything.

[gazzerr]

True now that you say that I think the issue was that it was improperly grounded rather than not grounded at all.

Here is the thread. Probably worth a read for stuff to check for.

Oxygen sensor relay - discrepancies