Another_User

Ok, I am having a bit of an issue with my fuel trims, and normally I would attribute it to the ported MAF, but I saw the same issue before I stuck the ported ends on. As soon as I start to decel my trims go positive (unless I force my fueling way rich). They are going positive at the same airflow that they would be 0 or slightly negative during cruise. I tried throwing some timing at the base timing tables thinking that the difference in timing could be throwing my trims off, but the swing is way too far for me to be able to blame on timing. The only thing I can think of is that with the throttle closed on decel one of two things is happening:
1) slight vacuum leak (just changed my PCV, so that is not it, and everything else looks completely tight. I even verified PCV for proper operation and it closed under vacuum)
2) airflow is biased to an area of the MAF in a way that causes the MAF to read lean on decel (I think this is actually it)
My MAP is pretty darn steady, so I doubt there is a leak. So what are my options? Is this something that DFCO is used to mask on MAF tunes? It explains why my surging and bucking were way down on my SD tune. The trims never went wacky like this. Anybody have any thoughts?