Running rich, PCV?

[xeno]

I noticed my car (2008 Avalanche) is running a bit rich. The LTFT values are under -10; bank 1 is around -15 and bank 2 around -12.

 

I checked various things (with scan tool), like the MAP and MAF values, fuel pressure and removing and plugging the vacuum hoses.

 

When I took off the oil filling cap (or when I remove the 'PCV fresh air tube' and plug the hole) the values increase for both banks with around 10%. What meant the values are in the acceptable range. Is this normal or indicates that my PCV valve is broken?

[CamGTP]

If I remember right, there isn't like an actual valve but more so a baffle built into the driver side valve cover for the PCV system. There is an updated part number for vehicle that had bad oil consumption.

 

Can your scan tool also read ethanol/alcohol content from the computer? It's somewhat common to have the virtual flex fuel feature go wonky and report false data to the computer. Say your local area is up to 10% E content in the fuel but the truck is reporting 20-30%, that can skew the fuel trims like you see here.

[xeno]

The PCV valve is indeed part of the valve cover. 

 

My scantool reports nothing for the alcohol pid. I do know it is based on an algorithm, where (the model) before used a sensor I believe.

 

I just wonder if the behaviour (rising of LTFT when oil cap is removed) is normal or indicates a problem?