Quote Originally Posted by Kitch View Post
My 8625 PCM using OD has some similar and some different DFCO values, yours make more sense to me.

I have AFR surging during deceleration but it's not overly noticeable in the vehicle. Your experiment with trying open loop made me think about looking at an old log I took with closed loop off. Sure enough there are no large AFR swings when decelerating in open loop compared to the large swings when in closed loop.
It will be interesting to see what you find to be the cause, I suspect it will help solve my issue as well.
I would look at your idle proportional gains and proportional duration. The gains and durations are designed to make the air fuel ratio swing rich and lean for proper cat operation. When you increase the fuel delivery by upping the pressure or changing injector size and add transient time by moving the 02 sensor downstream from the stock location you effect these.