Its unmetered air. Manifold vacuum draws air in through the crankcase. LTFTs get too far out of whack and trips the lean code.

 

So you think it's pulling air through the rings while the engine is running? Idk any other way it'd be pulling air from the crankcase. I don't think that's the issue

 

Lol no, the air doesn't actually come from the crankcase, it comes from that breather because the crankcase now has an opening to atmosphere. Air gets drawn through the crankcase. Its not a huge problem, but the computer noticed something different. The solution is to simply adjust VE for the breather, possibly some idle settings. I have seen this issue on both MAF and MAF-less vehicles.

 

But what sensors are actually monitoring crankcase air? There aren't any. I just don't see how the O2 sensors or MAF sensor would be affected by venting crankcase air since this air shouldn't be making its way into the combustion chamber.

The only thing I can think of is the PCM is calibrated to account for air being pushed in through the PCV system, which it is no longer getting because it's capped off. But wouldn't the PCM adjust itself for that? Or is it a big enough change that it would need to be tuned for.

 

Sent you a PM

 

Sucks to hear man. I'm glad our deal went smoothly which is why I was as up front about everything possible on the wrx, and I can't say enough how up front you were with the truck. Even with it down, I'm still in love with the damn thing, and I've sold vehicles in the past over less lol.

 

Smokeshow is correct... basically what that does is create a vacumm leak... Since the PVC is sucking on one side the breather is letting in fresh unmetered air.

 

I forgot about this little guy here. Thanks for reminding me smokeshow

 

Still a issue if the TB port is blocked off? Just curious I have had the pass cover vented, the TB blocked of for some time now. Maybe it is diff under boost, as it will blow out there.

 

If its set up that way, there is a pressure difference between your crankcase and cylinder under light load while the manifold is in vacuum, so its prone to drawing oil up past the rings. In boost you're fine because the crankcase pressure can escape.

Maybe we need to get a good PCV thread/sticky going?