Ok so I have a 93 impreza that spun a bearing and went and purchased a 96 legacy 2.5 dohc engine for the swap...with the ej18 harness and computer the car started fine but idle was at 2500 so I put the 1.8 throttle body back on and idle jumped to 3000 so went and purchased a complete harness.and computer and there's a lot of plugs that don't clip to anything in the car...my cars been down a month and looking for any and all help possible cause I need to have my car running so I can have it back to go to work...thanks
Put the 2.5 throttle body back on, clear the ecm memory, then start the car. let the car idle for a while and see if the idle speed goes down after about 5 minutes. If not, maybe the ej18 computer is not compatible with the ej25 engine, due to voltage signal differences.
did you get a new harness and computer for the engine, or the car?