I would check the impedance of the shift and the lockup solenoids.  I don't have
a service manual but I think they should be in the range of a few dozen ohms.
If they are ten times that, they must be replaced.  If they are within
specifications, you might have a flaky transmission control computer.  It
wouldn't necessarily be indicated by any flashing dashboard lights.  You should
also check for any flashing diagnostic lights on the computer itself when you
first apply power with the ignition switch.  I think you have to peel back a
little flap of carpet under the passenger's left foot to see the light-emitting
diode on the module.

--
Chuck

I bought a 91 EX and 92 LX from a local towing yard for $2000 for both.
Not a bad deal I think.  The 91 has brake light issues that I am
currently working on with the help from this group and needs a new
passenger side mirror in order to be road legal and pass the state
inspection in VA.  The 92 is a different story.  The engine runs like a
champ but the transmission is acting kind of crazy.  When the car is
cold, the transmission works like it should.  Once the car is up to
normal operating temps, it seems to have some problems.  When I am
driving, it will drop out of gear.  I pull off the side of the road,
turn the car off, wait 5 seconds, turn the car back on and it works
fine for a little while then does the same thing.  If I am sitting at a
stop light and go to accelerate, the car drops out of gear and i do the
procedure mentioned above and it works ok for a little while.  When I
go to drop into passing gear, it drops out of gear and just revs then I
have to stop and do the above procedure again.  Needless to say it
really is a PITA.  There is also a high pitch whine coming from the
transmission side of the engine (possible torque converter).  Any
suggestions as to what the problem may be?