2003 Honda Accord ex problems. Need

Me and my dad recently bought a new engine for my 03' Accord and we installed the new engine and the car starts up but after a couple minutes of letting it run the engine will start revving and we can't figure out why. Any automotive mechanics or technicians know why this is happening and how can I fix it.

Read more: https://hondanews.net/accord/2003-honda-accord-ex-problems-need.html