Labda Sensor

[steve-V8s]

What does the Lambda sensor measure to work out if the fuel is weak or lean ? in fact my question really is if the engine is really really rich could a wide band be confused and report lean ? just fitted different injectors and expected it to be rich, it smells rich but the wide band says off the scale lean.

[Bluebottle]

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Any manifold leaks will give a false reading (which mine is doing currently, over fuelling cos the lamdba is reading high oxygen content due to a blown gasket).
Also the 14CUX fuels the LH & RH bank seperately so if one of the narrow band sensors is faulty or reading incorrectly this would make it fuel incorrectly and not necessarily picked up on your wideband, cos thats only readinbg one bank (took me ages to figure out i had a duff narrow band sensor on the other bank cos i was reading the wideband reading for the other bank ).

[blitzracing]

Misfires also show up as a lean mixture, as the fuels not burnt, and theres lots of spare oxygen in the exhaust that the lambda's mis read. The ECU will then put in lots of extra fuel to compensate, which of course does not fix things, but just soots up the plugs.

[steve-V8s]

It is definitely misfiring and is without doubt running very rich which is what I expected with increased fuel pressure and different injectors. I was just a bit perplexed as to why the Wide band was reporting off the scale lean. The ECU will be making no adjustments at the moment because I am running Open loop on a fixed map.

As understand it the sensor normally determines the amount of oxygen by seeing how much is available to be burnt in the gas. If it is lean less of the oxygen is burnt so the sensor finds more is avialable to burn and reports lean, as you have suggested and my small brain didn’t consider is if it is not burning any of the fuel it will or may also report lean when it is rich.

Thanks for that. It always helps to have a second person think about a problem. If only I had a Hydrocarbon sensor as well....