Would this valve be considered disfunctional if its constantly knocking, relatively loud? I can feel it in the vacuum lines pulsating...it speeds up and slows down by itself regardless of engine rpm...i just ordered a new check valve thats part of that system that is completely disintegrating and obviously needs replaced. I've got evap codes P0441 and P1136. Figured I'd start with the check valve and go from there. But I also assumed that if it was the check valve, spraying it with carb cleaner would make the engine cough...didnt happen. Just made the n80 valve start knocking. I'm also having the notorious hard starts after filling up with petrol. I don't ever top it off after the pump clicks off. Gotta get these EVAP codes figured out...this CEL is driving me nucking futz! Thanks in advance gentlemen. Here's a picture of the "suspect" check valve.

 

I have a 18t, and just spent all day at my dads shop fighting p0441, and my lean code. To make a long story short, I used brake cleaner, and found no leaks, but the vac lines were clogged/broken. So if you haven't done so, replace all of them. That check valve looks melted shut, so just remove it, and blow through it. It should only flow one way obviously. Replace in the same direction too. My n80 pulses randomly so I wouldn't say its bad just yet