Weird hiccup with 97 tercel

My Tercel has been doing a hiccupy-jerky thing at about 50 mph–can’t tell if it is shifting gears at the wrong time or having a temporary loss of power. So far, have had the spark plugs and wiring harness replaced, the ignition coils checked (it wasn’t them), the crankshaft sensor replaced along with the timing belt, and the front brakes replaced (right caliper was frozen). Problem disappeared over the winter, but now that it is warmer, has reappeared, in spite of all the fixes above. Any ideas?

I think you need to get the fuel pressure tested and the fuel filter checked. The fuel pump may still be operating but it may be below the pressure needed to let the engine run properly.

Dist cap and rotor, recheck connections at coil and dist