Wandering AFRs and crazy fuel trims at partial throttle

Update;
Finally got around to checking that check valve. i didn't run with it plugged yest but I pulled the line and there is not a check valve in that line at all. I did check the other line next to it which does have a check valve in line along with the purge solenoid. I checked both of those and they were good. Pictures are attached. Should I just get a check valve and put it inline on the upper hose?

 

Dont change things until you know that is the source of the problem. You need to plug the intake port and see if the situation improves. As for right now its just a hunch. If the problems are because of the power brakes system, plugging the intake port will answer that question. Then you need to figure out what part is the culprit. There is a possibility there is no check valve, I could be miss informed.

 

I hear you there, I am going to plug it and check for improvement before doing anything. I did find diagrams and posts talking about a check valve in that hose though. I will update after plugging and testing later.

 

Update:
I clamped that line and took it for a drive very carefully. That seemed to make little to no difference in the fuel trims.

 

Are you still going lean with brake application, still having the same issues? Or do you mean that nothing changes when the brakes are applied?

 

Yes I see that but it is only happening really at idle. When I press and release brakes (idling while stopped) the AFR gets rich and then lean and takes a couple of seconds to recover. The condition is more random seeming while driving, almost solely in partial throttle.

 

What are you running for a BPV? Can you swap it out for another? It is normal for the AFR to richen when the brakes are applied, the booster is putting an air load on the engine which is post MAF. Something else is the issue making it hard for the computer to maintain proper AFR.

 

Ok that makes sense I didn't realize. And I am running a tial vta knock off with the stock spring replaced with a proper one. I don't have a stock or one I could swap with right now but I do have a block off plate I can try sometime this week. I have checked it pretty well for leaks when I cleaned it a couple months ago but I could disassemble it and clean it again to check.

 

The blow off valve is still properly sealed and functional.

 

Although Im not a good log reader, I tried looking at the logs in the OP. I see your LTFT runs between 0 & -10. Although that isnt optimal and should be tightened up, its not grossly out of whack. Its bad, but not that bad. Have you spoken to your tuner?
Your STFT do fluctuate a lot under normal conditions. I didnt see - to + 25, not saying you havent seen it but it isnt in the logs.
Is the idle or drivability affected? Or just the readings and fuel economy? You changed the MAF connector, what lead you to that action?

 

So as far as I know you are correct, this leak isn't the end of the world but it is something that hasn't always been present and as such it bothers me. I haven't talked to much to my tuner about it recently, Andale927 is an old buddy and college roommate of mine, a trustworthy tuner but that's also just his hobby, he's been busy with work and life lately so I haven't really been able to get a hold of him.

Last time we talked about it he didn't seem too concerned but I want to fix it if I can. I want to self tune my next revisions and self tune my SSC for the 6th port kit and I don't want to have to worry about this issue making tuning more difficult or masking issues.

As far as the effects go, the car feels slightly more sluggish and less responsive (spooling slower possibly seemingly running slightly rough out of boost). The biggest observable things are the trims and the fuel economy and the occasional startup/idle session where the AFR is unable to settle at 14.7.

I replaced the MAF harness because the old connector was loose and I was suspicious that it was causing a bad connection with the MAF, it was like $12 from NAPA and I am good at soldering so I said why not for piece of mind. Though it did not end up making a difference unfortunately.