I have a problem recently in my C5
Some times when its parked for long time in hot weather it will go rich almost 2 to 3 complete points
Like 12 AFR in all places for short periods and come back to 14.7 after 2-4 Min
-fuel pressure steady
-comanded AFR is steady
-volatge is steady
-MAP is steady while idle before and after the problem
-problem happens in idle or while cruzing every where in the VE table by almost the same amount 15-20% extra fuel
-the car has two wide bands in each bank and they reads the same so its not bank to bank related or wide band issue
-The car is tuned SD open loop so I think there is some thing wrong with my EVAP system makes it go that rich
Any suggestions to trace the problem