O2 sensor indicating lean, running rich

MagneB · Post by **MagneB** » 17 Nov 2024, 01:12

Thanks for letting me into this forum, highly appreciating all the knowledge collected. My entrance to the Volvo world has been quite steep, buying a cheap car with an ideling issue... Probably just injector/plug/coil they said.....

We have now discovered that O2 sensor is indicating lean at idle, but car is running really rich with a smell of unburned fuel. Spark plugs getting black. When the rpm increase the reading seems normal, even quite fine.

The famous Magnetti Marelli ETM is also throwing codes so it will be converted to contactless, hoping for an improvement....

The car is an 2001 S60 2.0T, really nice looking and I would love to bring this back to life. Any suggestions is appreciated

dikidera · Post by **dikidera** » 17 Nov 2024, 02:39

Possibly ETM that is directly affecting air flow.

Post by **chrism** » 17 Nov 2024, 12:59

It would make sense that if the O2 sensor is (falsely) reading too lean that the system would richen the mixture in reaction. Maybe try a new O2 sensor?? Also, have you connected a fuel pressure gauge at the injector rail to make sure the pressure isn’t running too high?

MagneB · Post by **MagneB** » 17 Nov 2024, 13:38

Also found out today that PCV was quite blocked, and may never has been serviced as it had the original fitting to the lower hole in the block (fitting with two torx).

MagneB · Post by **MagneB** » 25 Nov 2024, 11:07

chrism wrote: ↑17 Nov 2024, 12:59 It would make sense that if the O2 sensor is (falsely) reading too lean that the system would richen the mixture in reaction. Maybe try a new O2 sensor?? Also, have you connected a fuel pressure gauge at the injector rail to make sure the pressure isn’t running too high?

Thanks, will check fuel pressure once "contactless" ETM is in place.