5.3 to LY6 6.0 swap idle problem
 

Hi, hopefully someone can help with my truck project.
Its a 2005 Silverado with a LY6 crate engine swap.The LY6 has had the VVT removed.It was not equipped with DOD.The reluctor wheel changed to 24 tooth,cam sprocket changed to 1 magnet. The cam was changed to a Comp #54-424-11. 212*/.558 X 218* /.563 115 LSA.
The computer has not been changed or programmed,the intake and injectors are also from the LY6.The 5.3 knock sensors relocated to the block.It has long tube ARH 1 3/4 headers and cats.New 02 sensors that are working. All emission items are in use. I also had to use an interface box for the T/B from Torque Rush (allowas the 8 pin T/B connector to fit the 6 pin T/B.)The problem is that when in closed loop,the idle will start to lope and the intake vac falls to 12".I checked what I could with a tech 2 scanner and found that the LTFT for both banks is reading -5% to -8%.The STFT `s are around 0%. I tried an external vac source for the map,with no change. Also when this occurs it will set a 300 for random missfires,that miss is on all cylinders at different times. If I remove the oil fill cap,the LTFTs drop to 0% to -1%.The idle also straightens out.The intake vac goes back to 16-17". The miss fires are gone.Does the ECM need to be programmed for the injectors/engine swap? Sorry for the long post. Any help would be appreciated.Thanks,Bill