S60 2.4 NA RPM flactuation ? (o2 sensor suspected)

[minkov89]

Hi there. I am driving S60 2003 year 2.4 NA 140hp with manual transition. The Volvo is with the facelifted ETM (not the problematic Magnet Mareli)

I have the following problem: when I driving with more than 30-40km and switch from gear to neutral very often RPMs start fluctuating between 500 and 1100 and sometimes the car dies. Also when coming to a full stop RPMs drop rapidly to 400-500.

First I suspected the brake booster so I have changed it with a brad new genuine ATE - the problem remains, no change.

I have cheeked for vacuum leaks but everything seems to be fine.

MAF is cleaned and cheked with VIDA seems to work fine.
ETM is also cleaned.

So I started to look at the live data. LTFT is 0.92 which means -8% correction. It means the car running rich of fuel but it does not seems true because there is no detonations in the exhaust, the exhaust pipe is clean and there is no black smoke. (All this characteristics of rich mixture are not fulfilled)

So I relay suspect the front heated o2 sensor. It is still working but seems to be lazy and not very correct. I have uploaded 2 videos. On the first you can see how lazy is the first o2 sensor, there is periods of 2-3 seconds without change of the parameters. As I know it should make changes at least ones a second. I think it also misleads the ECU or just is two slow and the ECU create not perfect mixture. It seems this is the reason for the strange fluctuation of the rear o2 sensor.

What do you think, are those two o2 sensors indicate correctly? And is it possible this to be the reason for my problem?

https://www.youtube.com/watch?v=viY4qg-7EFk

https://www.youtube.com/watch?v=HDHWVaKq2Dc&t=11s

https://www.youtube.com/watch?v=oYdhh-6Wq2o&t=183s