D15b 3 stage vtec, Y8 IM, and p2j003 ecu.
I just swapped my P2m to P2j003 and wired the (2nd vtec to A21 and O2sensor 1 wire to D7) ECU pinout. Now the problem is when cold start engine revs high then goes down to 2-300rpm sometimes dies. Its not idling good like the previous ECU(p2m).
But once the engine is warm, its drives so good. Im also using hondash bluetooth app to monitor my car performance, AFR reading is 17 to 19 when reaches operating temperature. is it normal for this engine?

 

Any CEL's? It sounds like you have an issue with your IACV.

Are you running a wideband oxygen sensor? If you are just using the stock narrowband sensor, the AFR readings you are seeing in Hondash mean nothing, as a narrowband sensor only puts out high/low voltage.