I'm officially desparate for help.  I've gone through numerous replacements,
swaps, fixups in an effort to get this problem fixed.  Nothing works!  It is
a 1990 2.1 Westy.

Here's the problem:
* Starts fine when cold.
* When it warms up it blows black smoke real bad.  Too rich.
* It has the Vanagon syndrome fix (that 8" long resistor thingy) on the AFM.
I remove it while the engine is stumbling and then it runs fine at about
1000 rpm.  No black smoke.
* With the engine stumbling, nothing attached the the AFM, then I take the
resistor thingy off the main wire harness the stumbling returns.  Black
smoke.  Put the resistor back on the harness, runs okay.  This is done while
NOT attached to the AFM.
* When I turn off the engine. Plug the harness into the AFM (with no
resistor thingy), it runs fine for about 60 seconds and then stumbles again.
Black smoke.  With the engine still stumbling, I take the harness off the
AFM and it idles fine.

In an effort to fix this (for the last 2 months) I have done the following:
* new AFM
* new Temp II sensor
* new fuel pressure regulator
* new ignition wires
* new oxygen sensor
* new fuel filter
* new resistor thingy (Vanagon syndrome)
* rebuilt the throttle body and switch
* replaced ECU (second hand - told it was working fine)
* replaced idle control unit (second hand)
* cleaned and soldered all ground wires, new eyelets
* added new grounds to the right side of the engine and to the AFM
* tested the idle stablizer (okay)
* tested the wiring harness to the ECU (okay)
* tested timing (ok)
* air filter is fine

All of the above does not help.  This problem has drained me of patience and
$.  ANY ideas would be greatly appreciated.

Laurence Smith
Hamilton, ON