I have recently been getting a CEL of P0175 - System Too Rich (Bank 2) and P0172 - System Too Rich (Bank 1). I recorded a few datalog sessions and looked at my STFT (Short Term Fuel Trims) for both banks. These CELs ONLY happen under idle.

This thread will explain in more depth:
https://www.6speedonline.com/forums/...threadid=30697

Below is my datalog graph at idle. The two valleys are where I quickly revved to 3000rpm and then let back off the throttle. As you can see, BOTH of my STFTs are in the -16 to -22 area while at idle.

Something to note:

If the MAF is affected: This means Long Term Fuel Trims will learn lean (negative) corrections at idle and learn rich (positive) corrections at higher air flows.

I have noticed this very pattern. After coming off of a hard drive, my LTFTs are typically postive (sometimes as high as 4, 5, or 7). As can be seen in the log below, at idle, the STFT corrections are negative as it is trying to get the positive LTFTs back down.





Opinions? Thoughts? Does it seem more like that MAF to you?

 

It looks like the MAF to me. I guess it could be a leaking/open evap cannister purge valve, allowing rich gas tank fumes into the intake. It seems the MAF is a common failure.

 

How easy is it to reach the EVAP cannister? These logs seem to rule out a leaking injector I do believe.

The MAF doesn't always go off, however. It seems to trip when there is a lot of humidity/when it is raining. Perhaps the MAF is getting coated with fine water droplets?

 

could be.. is tehre anyway or do u have acces to anoteh turbo in your area maybe u can swicth maf's or something.. that can easily tell if the item at fault is your maf or not...

 

Good idea!

 

Now, about that EVAP cannister. How easy is it to get to?