you sure it was a 97?

you know that is an OBD2 engine right? so if it came with the stock harness and the stock ECU, then it is pissed off because you are missing an O2 sensor.

technically, you could have installed an OBD1 harness onto that OBD2 engine and used a obd1 ecu.

So you have an S14 MAF? an S14 ecu?