You Volks are really great! I can't tell you all how much I appreciate your
help. I believe I am finally getting the big picture on the FI system.

The problem I am facing is that the engine runs rich at idle in "open loop"
condition (O2 sensor disconnected). I tried to adjust this with the AFM
screw but it wouldn't drop down far enough. My next step WOULD be to adjust
the spring tension inside the AFM, except that I can't be sure at this point
that I have no leaks in exhaust, vacuum, or fuel injectors. I am reluctant
to break open the AFM simply because I think that Bosch would have
calibrated it to a properly functioning engine. It seems like they would
have made the spring accessible if they expected it to be adjusted in the
field. So I MIGHT be able to compensate for whatever is leaking with spring
tension, but it's better to find the root cause of the problem.

Tomorrow I will measure the compression, fuel pressure, and vacuum. I plan
to look for exhaust leaks, although I have no clue how to find them. I will
check every wire that connects to the chassis ground and to all the FI
sensors/switches.

One thing that I didn't mention before is that I have a leak in the coolant
system (surprise!!) and my antifreeze concentration is likely to be way too
low since I have topping it off with straight water for some time now. I
read somewhere on the web that emission control is "impossible" with the
wrong concentration of antifreeze. So I will drain the system and refill
with the proper ratio (not saying what type of antifreeze for fear of a
flame war!). I'm very curious to see if this changes my emissions.

I may end up putting in a new cat converter before all is said and done.
That feels too much like defeat tho!

Mike Frost
86 Vanagon GL "WasserLeaker" aka "Object of my Obsession"

P.S. Can I be sued for using the word "Volks"?