Rep Power: 0

I have a 93 civic ex coupe 5spd...put a 95 engine in it...was running fine then all of a sudden it starts but wont idle for long and shuts down...already changed the fuel pump...checked all potential issues, spark, etc...concluded it might be the ecu needing replacement...since all of the car is 93 except the engine do I need to replace the ecu with one from a 93 or one from a 95?... or maybe it doesnt matter what year?

 
Rep Power: 511

Yes and no? As long as all engine specs and sensors are all cross compatible, should be fine

Case in point, 01-05 civics (yes, I know you're talking 93-95), they all use the D17 series engines, however for 2004-2005 model years, Honda switched to a wideband AFR sensor from a narrow band O2 sensor used the 01-03's. Without also changing the upstream sensor to a compatible one, you wouldn't be able to use an 04-05 ECU with an otherwise factory 01-03

 
Rep Power: 367

If the ECU is looking for something that the engine or installed sensors do not have, it will cause a limp mode (not stall)
Like, if it is a VTEC ECU but the engine does not have it, yes, it will go into limp mode and CEL will light
If it's a VTEC engine using a non-VTEC engine, VTEC will not engage, but ECU is happy.