Mazda 3 - Faulty o2 sensor - or something else?

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Fri 18 Jun 2021 13:33
Mazda 3 - Faulty o2 sensor - or something else? - NyrBrian

I have a 2011 Mazda 3 1.6 Petrol. Around 2 months ago I got the dreaded Engine Management Light. Fault code came back as o2 sensor, running lean.

The mechanic cleared the code and didnt do any work. I used Wynns lambda cleaner on two tanks and since then the problem has been intermittent.

Overall in 2 months, I've had the warning light 5 times, and each time the exact same scenario has been at play. Sitting at traffic lights!

The RPM counter seems to dip from 750 to around 400-500 and then light comes on, at the same time.

My initial thought was get a new sensor, but the mechanic I use is reluctant to swap it as it might not necessarily fix the issue with erratic idling.

Could this be faulty throttle body? anything else exhaust related?

Im planning on going to a different garage next time, but id like a bit more background knowledge before I go.

Thanks in advance for any pointers

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Fri 18 Jun 2021 14:32
Mazda 3 - Faulty o2 sensor - or something else? - elekie&a/c doctor
Possibly neither the throttle body or lambda sensor are faulty . These suffer with inlet manifold gasket leaking which causes excess air into the engine.
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Fri 18 Jun 2021 15:22
Mazda 3 - Faulty o2 sensor - or something else? - NyrBrian
Possibly neither the throttle body or lambda sensor are faulty . These suffer with inlet manifold gasket leaking which causes excess air into the engine.

Thanks for the heads up.

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