Bank 1 and 2 O2 sensors running rich?

Tiny
AKSELNABOZNEY
  • MEMBER
  • 2010 NISSAN ALTIMA
  • 3.5L
  • V6
  • 2WD
  • AUTOMATIC
  • 180,000 MILES
My car listed above has been having problems related to the engine running rich. It used to be misfiring and was fixed with multiple sets of new injectors and spark plugs. Yet the engine is still running rich and idling roughly. We have replaced almost everything to do with the fuel line and system, evap solenoids, every rubber tubing piece, new intake gasket, cleaned throttle body, new O2 heater unit sensors twice, new MAS, ran a smoke system through the engine and found no leaks, replaced PVC valves and cleaned/ inspected every inch of the engine. I am curious if it has to do with the ECU and ECM systems or any voltage issues.
Any ideas to what the issue could be related to?
Thank you.
Thursday, February 20th, 2025 AT 5:14 PM

1 Reply

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 50,271 POSTS
The idling roughly is the clue, if the engine is misfiring it will push the long trim lean which will cause the short trim to be rich. Let's do a compression test first to make sure the engine is in good shape, or we will be chasing our tails.

These guides can help:

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

and

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

Please go over these guides and get back to us.

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Friday, February 21st, 2025 AT 10:37 AM

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