First look to see that the 3 wires that enter the distributor are properly
connected.You can remove the wire bail and pull the  plug out. Peek inside
the socket and look for 3 contacts that are all evenly seated in the bottom.

Go wiggle or remove/replace all the electrical connections .Like the hall
generator on the fire wall,the AFM connector,coil wires,ECU plug.

If you do have VS, start with adding a ground wire to the AFM and frame.
Next, remove the AFM(EZ) and solder in a tanatlum capacitor as per Tom
Carrington's repair proceedure in the vanagon list archives.

I understand that the little board inside the AFM,that the contact sweeps
over ,has a wear adjustment. The little screws can be loosened and the
board adjusted so that a new wear area is now in contact with the needle.In
practice, these little screws are far too tight to loosen up on(my
experience).I have heard of others being successful here.

                                       Roger