1990 Accord transmission won't engage (or stay engaged)
 

I have a 1990 Accord LX that started acting up this morning. The transmission would not stay engaged. If cool, the car would work for a short period (1 mile or less) before it would disengage again. The vehicle behaves as if in neutral once the problem begins.

I have visually inspected the transmission control unit TCU and the capacitors and resistors looked ok. We also removed and tested the transmission selonoids (both units on Both the lock-up control and shift control solenoids). There are no lights displaying on the dash to indicate the type of trouble.

The behavior continues and I'm confused.

Any suggestions on troubleshooting/repair would be appreciated.

Thanks,

Brad