Jay Honeck wrote:

Our best guess at this
point is that it's something inside the right rear door -- but I haven't had
time to rip it apart to see.

A friend of mine worked on the warrantee line of a Datsun dealer back in the
late 70s. One day he got in a car with the same complaint you have. Opened up
the door and found an unopened can of soda with Japanese lettering. Near as he
could figure, the factory had a rule against food on the assembly line, and some
manager happened by just as one of the workers was about to open the can, so he
stuffed it in the door and put the panel on.

Al said it didn't taste very good to him.

George Patterson
Give a person a fish and you feed him for a day; teach a person to
use the Internet and he won't bother you for weeks.