Help with O2 Sensor Issue with Holley HP EFI

[ROKN69]

Good evening, everyone,

I have a situation where the O2 sensor reads lean (24-28 to one) when it's not. The car is dumping fuel and flooding itself out.

We have purchased 2 additional O2 sensors (now have a total of 3). We have tested the wires between the ECU and the O2 sensor connector. I believe there are a total of 8 (including one shield wire ).

In the past week or so we have found and fixed several nicks in the harness wire between the ECU and the O2 sensor. Each time the car runs fine for about an hour or so after the fix, but then it goes pig rich again because it somehow quits reading the O2 sensor.

Yesterday the car ran fine for an hour or so (lots of idle time in traffic) and then the ECU said it lost the O2 so it went pig rich and quit running. I had it towed to the shop this morning and, after several hours of taking the O2 sensor harness out and messing with the pins, and checking for continuity and resistance checks (all checked out fine), we replaced all the wires between each connector as a last ditch attempt to remove any concern over the wires in the harness, but it didn't help. We did this because we don't yet have extra pins or an actual unterminated harness to work with. We won't get those parts until this coming Tuesday.

Our plan is to replace the harness with a new one, and make sure we have new pins going to the ECU. We hope this works, and if it doesn't we are out of ideas...

Does anyone have any experience with fighting with an O2 sensor on the Holley HP EFI setup? If so, can you shed some light on what we might be missing?

I'm beyond frustrated at this point. I just want my car to run properly, and do so reliably.

Many thanks in advance for your help in diagnosing this issue!