My 1984 Vanagon has a problem that I have not been able to solve.  When driving or standing still at about 1800rpm the engine experiences about two seconds of overly rich mixture (smoke can be seen from the rear view mirror) then runs correctly for about 15 or 30 seconds and then repeats this performance.

I cleaned and reattached the ground wires which attach to the exhaust manifold on the engine.  This produced no change in the performance.

I have replaced the temperature sensor several months ago.  This smoothed out idle.

I replaced the oxygen sensor about a year ago.  Did not use Bosch.

I replaced the computer and the air box when the new engine was installed about 20K miles ago.

Wires, cap and plugs were replaced about three months ago.

Any ideas will be appreciated.  Can a dealer connect this model vehicle to an analyzer and isolate the problem? There is some type of plug on the alternator that may be for this purpose.   Please reply to this e-mail address as I simply can't keep up with all of the Vanagon messages on the server.

Thanks in advance!
George
Columbus, GA