O2 sensor heater circuit cause injector-cut-like symptoms, anyone else?

[Steptoe's photos]

With the simple disconnection of my SF5 Forester's 3 wire oxygen sensor, I have eliminated the injector-cut symptoms that have both baffled and crippled the beast twice now, 2,000km/six months apart. Injector cut occurs between 2000 and 3000 rpm making it undriveable, not able to get it above 3,000 like this.

The first fix took me three months of check, test, swap, tinker, collect manuals in paper form to study to finally find the "main relay" had finally died, giving me a no start result. Replacing it, took away my fuel cut symptoms. Swapping in another did not fix same , six months down the track.

The sensor's heater power shares the same circuit as the fuel injectors power supply, so it seems that the as yet, unidentified internal issues of the O2 sensor were causing my injectors to not squirt fuel momentarily under light load. Heavy load is not possible. The only thing preventing the cut out issues is the cold start circuit period of faster idle, fuel enrichment time of about three minutes - perfect for discovering trouble minutes from home on a cold start

I am sure mine is the world's first of this reliability issue, so no cause for concern by anybody else. For this possibility to occur, I can see it is not a smart idea to power something so critical as injectors on the same circuit Murphy can have his fun with an O2 sensor !!

Edited December 13, 2023 by Steptoe's photos

[el_freddo]

Have you thrown a new O2 sensor at it to see if this resolves the issue like you think it will? 

Fingers crossed that’ll sort out the issue. 

Cheers 

Bennie

[Steptoe's photos]

18 hours ago, el_freddo said:

Have you thrown a new O2 sensor at it to see if this resolves the issue like you think it will? 

Fingers crossed that’ll sort out the issue. 

Cheers 

Bennie

I have thrown anothery at it, from 9/95 Liberty as it looks nice, plug and wiring is the same, just it has long slots, the original has lots of holes to breathe through.

Turning the place upside down to find my spare sensor I put aside in a safe place. It is the same.

Guess what - I do not get a CEL for O2 sensor even being unplugged. I never got a hint it was not happy, possibly that the input side was happy and working fine to give me 7.5 litres  per 100km . I think it had to be some sort of issue in it's power side interfering somehow with my injector power supply, not tripping 15A fuse # 11 behind coin tray ( Mum, what is a coin ?? " or the 30A baby in the engine bay.

I do now, however have a code 2-6 for the air temp sensor which is working, right down to the ECU plug.

A piece of black tape going over the CEL until ECU sorts itself out again on this one.

Delete diagnostic mode won't knock it out.

Edited December 15, 2023 by Steptoe's photos