Another piece for the puzzle... happened as described several years ago. '90
Syncro. Symptoms identical. Switching ignition on/off no effect. Could go
months between occurrences, or sometimes it would happen two days in a row -
couldn't find any correlations. Disappeared as mysteriously as it appeared.
Until two summers ago - after driving through an automatic car wash it came
back, lasted about 20 minutes, then passed. Now I can pretty reliably
reproduce behavior for $5 at any automatic car wash. The problem does not
occur after hand washing, during rainstorms, driving through standing water,
or even after thoroughly soaking everything with a hose in an attempt to get
it to happen. Go figure.

Doug Fitz-Randolph
Freeport, ME