02 sensor issues

2011 HONDA CIVIC
81,000 MILES • 1.8L • 4 CYL • 2WD • AUTOMATIC
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MARK.STACY
  • MEMBER
  • 1 POST
Car runs without o2 sensor connected. With 02 sensor connect gets rich condition and will not run well. 2 new 02 sensors have been used. It is the sensor that is right in front of motor.

Any ideas?

thanks
Aug 12, 2021 at 7:39 AM
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BORIS K
  • AUTOMOTIVE REPAIR CONTRIBUTOR
  • 836 POSTS
Hello,

By disconnecting the O2 sensor the engine management system (ECM) will substitute the O2 value with a pre-programmed value.

The most likely reason that your engine is running rich with the O2 sensor connected is that the O2 sensor is detecting a lean running condition and the ECM is trying to correct this by adding fuel.

A lean running condition can be caused by an intake system air leak, vacuum leak, exhaust leak or even by an aftermarket induction system.

Here is a guide on how to check for a lean condition:

https://www.2carpros.com/articles/repair-lean-mixture-codes-p0171-or-p0174-on-some-manufacturers

Please let us know how you get along

Cheers, Boris
Aug 13, 2021 at 6:20 AM
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CARADIODOC
  • AUTOMOTIVE REPAIR CONTRIBUTOR
  • 34,308 POSTS
Don't forget a spark-related misfire. Unburned fuel will be smelled at the tail pipe, but it's the unburned oxygen that will be detected by the O2 sensor.

Happy Friday to you guys.
Aug 13, 2021 at 4:40 PM