So what’s wrong with my car … they took the old impreza into the garage with the service manager muttering under his breath that it was probably just a loose fuel filler cap.
It wasn’t a loose fuel filler cap; I read my manual, and know how to properly tighten my gas cap.
This was confirmed two hours later when I was told that the computer indicated there was a problem with the tumbler valve. Having never seen this, my local dealership called the mothership. Subaru of America advised that the proper diagnostic measure was “to replace the whole assembly.” The scope of this isn’t entirely clear to me, but apparently this is a 1-3 day procedure at the dealership once they get the parts in. Joy.