Quote:
Originally Posted by blue62
you have a interesting situation there.
Backfiring into the intake would indicate a vacuum leak
The sound in your video sounds somewhat like a vacuum leak.
But on the other hand your low RPM fuel trims (RKAT) are negative values indicating a rich condition at idle. Vacuum leaks cause lean conditions at idle. Your mid to upper range fuel trims look to be positive values which you would expect under load at mid to upper RPM range. Adding fuel under increased engine load.
Porsche and or Durametric expresses fuel trims in a manner that I am not very familiar with so I could be off on what I think I see.
What are your pre cat o2 sensors doing at idle and again at say 3000 RPM???
If fuel trims are going negative at low RPM I would expect the O2 sensors to be showing a rich condition. Voltage above .500 mil volts then dropping as RPM increases and fuel trims go positive.
The sound in your video also (to me) sounds a little like a possible exhaust restriction.
Any chance the Cats are plugging up??
Don't know if I have helped or added confusion 
But those are my thoughts |
Hi again! You're absolutely helping and I appreciate it. OK, re: the exhaust, I have not done any troubleshooting there. What's the best way to know if my cats are plugged? I will do some searching and see if I can find some posts. Would the engine operate smoothly (more smoothly, still down on power) at higher RPM and experience the bulk of the issues at idle if the cats were plugged? Would I get a CEL if the cats were plugged? I'm interested in performing any suggested troubleshooting.
Regarding the RKAT and FRA data, your thoughts echo my own, which is why I was hoping I had a non-functioning fuel injector(s) (open at idle more than it should be going rich, but not delivering enough fuel at WOT resulting in lean at higher RPMS). I have some data plotted, I'm not sure how to get the paste in from excel, so I'll try posting some image captures of the data.
If anyone would prefer, I can take a shorter time snaps, to open up the plot a little more if the data isn't clear enough. Unfortunately, I don't think I have/plotted MAF voltage, but iirc, it was within Porsche specifications, thus I haven't replaced the MAF.
Thanks again for all of your time!