I have a 1997 Accord with the awful 2.7 v6 that’s knocking. I was wanting to do a swap over to the original 4 cylinder. I would assume if I change out the engine sub harness from a 1997 4 cylinder accord and change the ecu that should get me close. Anybody else down this and know what else I may need to do or change, main wiring harness as well?

 

You would need a lot more than that...The engine bays are completely different, dash harnesses/cluster differences, ECU, etc etc etc. You would basically need an entire donor car with a 4 cylinder and even then it would require cutting/welding mount brackets amongst other things. Might as well just get another car at that point.