What I see from this data is that the fuel trim is within an acceptable range even while I've got the pedal to the floor. It appears that the upstream sensors are doing their jobs (for the most part) although maybe tending to read more rich. The downstream sensors are trying to hang in there but appear to follow the trends of the upstreams - very much like the cats aren't working quite right.
Hello again Big_Red9,
The short answer is that once you get past a certain demand for power, on purpose the system goes from emissions-oriented
Closed Loop to performance-oriented Open Loop in what is referred to as PE (Power Enrichment) mode. Instead of trying to
achieve a closed-loop 14.7:1 (stoich) Air/Fuel ratio for minimum emissions, the computer reads all the sensors
(MAF, MAP, TPS, IAT, ECT, RPM, etc) and then sets the spark advance for max power (while listening to the Knock Sensor)
...and now fueling for a mid 12/low 13 A/F ratio goal.
In English, your O2 sensors are showing that your Open Loop operation is actually working as advertised. Pretty neat!
The abnormality is what happens directly after I get to normal highway driving after this heavy load event. The O2 sensors trail off to be almost the exact same readings that suggest an almost nonexistent level of O2. It's not shown in the attached pictures, but the O2 readings return to fluctuating after a few minutes.
Real strange! Hopefully this data is screaming something that someone with more technical know-how can hear. Thoughts?
P.S.
On this trip ol' Big Red also reached 160,000 miles so wish her a happy 160.
Again, once you're done flogging your faithful travel companion, your O2
sensors should start toggling again in part-throttle closed-loop mode.
EDIT x 2: If it took minutes for the O2 sensors to return to toggling post heavy demand
session, then this is not the expected behavior? I looked through your parts list, but
didn't see any mention of replacing the upstream O2 sensors? Any idea how old
they are? Or if you did change them, what brand did you use, and how many miles
are on them?
Do yourself a favor and get your own copy of the FSM, where you will be regaled with
descriptions about how all this is supposed to work. Meanwhile, hopefully some of our
crackerjack EFI tuning gurus will stumble across this thread and add their value - they
are fun to watch in action. Good stuff!
(Disclaimer: I'm an old carb guy, pretty comfortable with the underlying theory, but still
not quite yet sitting at the cool kids table with all this EFI/ECU/ECM/PCM/VCM mumbo-jumbo. :0)
But I'm confident that once all this gets kicked around and properly aired out that this
is gonna get fixed up to everyone's mutual satisfaction.
Thanks for the status update. No pressure, but I'm looking forward to
you being able to share some misbehavior data. And at some point, maybe
some individual cylinder misfire counts also?
Cheers --
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