O2 sensor diagnosis?

So it looks like you may have a fuel injector that is stuck open or leaking, I would remove all spark plugs and look for the one that is dark/black in color, this will be the cylinder that is having the issue.

P0176 on this model - Fuel Composition Sensor / Fuel Mixture Too Rich at Idle.

Please go over this guide as well, it shows what all can create a rich mixture code.

https://www.2carpros.com/articles/why-an-automotive-engine-will-run-rich

Please upload an image or a short video in your response of the spark plugs so I can see, be sure to keep them in order.

Hi Ken, first off thank you so much.
Plugs out as per pictured. Only one, cylinder 8, looks black with gunk on it.

Alright! yep #8 does not look good, lets do a compression test to make sure the cylinder is okay, then we can replace the fuel injector which should fix the problem. Here is a guide to help.

https://www.2carpros.com/articles/how-to-test-engine-compression

Let me know what the reading is.

Ok, need to get a pressure gauge and the injector is on order. :)

Nice!, you can rent a gauge set for free from AutoZone to do the compression test.

Ken, installed new plugs and air filter. Poured a can of injector cleaner in the tank and it passed smog with flying colors today. Appreciate the help.
Cheers, Ewan

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