...I know the source of the vacuum leak, with almost absolute certainty.

I've been hunting this thing down for a long time now and finally had the time off thanks to the holidays to tear into it. I started out by spraying around with carb cleaner, and it didn't take long to find the source. Revs began spiking when I hit where the UIM and LIM join up (the section with three bolts, with the bitch and a half bolt that's against the firewall), on the side nearest the front of the car.

I took the advice of many of the various P0171 threads and ripped the entire UIM off, checked all the vacuum lines going to it, replaced and reseated all the gaskets/O-rings, and put it all back together and ensured all the lines were good...but it still has a leak.

I've resigned myself from working on it any further today, as it's Christmas and we have family stuff to do. Judging by where it is, I have a couple of possibilities:

1) the bolts aren't tight enough (don't know if there's a torque spec for these...I searched every way possible to find one. I cranked them to "snug", as I didn't want to risk breaking the bolts or cracking the UIM)

2) either the plastic UIM or the LIM is cracked (doubt the LIM, because it's the stronger link and I've seen reports of the UIM being cracked in my searches).

Also, I noticed before I closed up for the day that there was a slight gap between the UIM and LIM at the spot I was spraying. I was able to fit a thin blade flat screwdriver into it with ease. This didn't look at all right to me, as I figured the two pieces should be flush, but again, the bolts are pretty darn snug. Opinions?

And to all, Merry Christmas!

EDIT, UPDATE: Just thinking back to when I had SSV ticking, is it possible that this could be causing the vacuum leak? It's in the neighborhood of where I was spraying and I seem to remember hearing a very muffled ticking while I was under the hood with the car running.

 

Bump.