One thing to do with a 19-year old vehicle is to clean EVERY electrical
connection and ground screw you can find.  Use a contact spray, steel wool,
and dielectric grease, and tighten down every ground.  I had many problems in
my '85 over the years that were complete mysteries until I cleaned all the
wiring.  A guy with a diagnostic computer showed me that my injectors were
screwing up every time the engine warmed up, because the expansion caused a
ground to lose contact.  Decades of corrosion can screw up lots of stuff, as
we all know.  Even if that doesn't clear up the problem, it will prevent more
problems.  Lots of luck!

Bill Marshall
85 GL/ Tiico
PHX AZ