KTuner.com

I have a 05 base rsx 5speed with jdm k24a swap motor is stock besides 50 vtc. Ktuner end-user is installed of the cars original ecu. I have been for the last 2 months trying to get a base tune from Derek at IMW motorsports who has been awsome as far as trying to help me figure this out. The problem is at idle about 2-5 minutes after start up the car starts to missfire and run very rough. You can watch the afr graph go from a nice straight line to looking like a rollercoaster. There are no codes present or no codes that have even shown up at all. I have the correct brand new denso 02 sensor in the car I even bought another one to make sure it was good. All grounds have been checked and verified good. Coils are good, new plugs, new map sensor, new tps sensor. Ktuner end-user was installed before the swap on the old motor with no issues. After the swap the issue with the idle started. I've ruled out so many things that pretty much all that is left is that maybe I damaged the ecu during the swap some how. Do I possibly have a bad Ecu. Any insight would be great. I've dumped a ton of time and money into trying to figure this out and have hit a dead end

Disable closed loop or disable the front O2 sensor and see if it is normal. If so you probably bought an 02-04 RSX O2 instead of 05-06.

I've double checked that as well. The car does idle normal with primary 02 disabled. The problem only exists with the 02 enabled. I've bought to brand new denso 234-9064 sensors which is supposed to be the one that is needed to the best of my knowledge. If you know of a different one I should be using please let me know. 2005 base rsx 5speed. Thanks for the help!

Honda Parts has information regarding the sensor. Xenocron also sells the correct one.

Thats where I got it from. Xenocron

Those are the suggestions we have for you. Seek professional help if you're unable to diagnose further by using datalogging etc.