I also have AE100-1993 car.My problem is little different.It start fine for 2,3 minutes and miss the engine.
I tried to get used 5A FE ECU, but i couldn't find.
Then I replaced with 4A FE, then the engine miss not more there. Engine is seems to running Ok.
But I'm not sure what side effects will come from this 4A FE ECU.