stft maxing out when clutch pushed in??

[2016SSlt1]

Is this a normal characteristic or any idea what is going on here? Cruising 50mph or so and depress clutch and go into neutral, Engine surges and sometimes stalls. I happened to notice when this is occuring the stft will abrubtly max out adding 29.7% right after even though o2s and wideband both agree that it is already a rich condition. I have reset the fuel trims and retested with same results. When I keep it out of closed loop it is okay so I think I am on the right track just have no idea why it would be so drastic with the stft.

2014 Camaro zl1 ported stock blower. id1300 injectors. built motor with btr stage 2 cam. stft max.png

[CaudleDynamicsLLC]

Hmm, odd. May be a long shot or off base here but simple to rule out: since its happening starting on clutch in, maybe log the status for DFCO and CFCO and see if its when either are switching from disable to enable then back? Obviously Clutch Fuel Cut Off should make the wideband go lean instead of rich, but may be something strange going on with the "timing" of them kicking in/out and then the fuel trying to catch up. (If you already have DFCO and CFCO disabled, or log and find they are not activating then all that ^ is null)

[pannetron]

Interesting. On my E67 tune, when the ECU enters Fuel Trim Cell 15, I see my LTFTs go very high, STFTs go near zero but vary, and my injectors go to their minimum pulse width, 0.8 msec. FTC 15 seems to be when I close the throttle and coast in gear. No clutch switch in my engine swap into a '66 Chevelle.

2022-09-15_11-08-39.jpg

[2016SSlt1]

I have disabled DFCO and CFCO but it didn't have any effect. I haven't logged fuel trim cell but maybe I will. Even if I can prove it is related to a certain fuel trim cell I am not sure how to go about correcting the issue.

[CaudleDynamicsLLC]

Interesting. On my E67 tune, when the ECU enters Fuel Trim Cell 15, I see my LTFTs go very high, STFTs go near zero but vary, and my injectors go to their minimum pulse width, 0.8 msec. FTC 15 seems to be when I close the throttle and coast in gear. No clutch switch in my engine swap into a '66 Chevelle.

2022-09-15_11-08-39.jpg

It looks like that is going into some sort of fuel cut based on the telltale spark timing drop to nearly nothing. It looks like it is pulling spark preparing to go into fuel DFCO/CFCO but doesnt yet shut the injectors off (spark transition time long, or hits minimum timing before DFCO timing, high delay value etc...) and that super low timing is probably causing the rich condition that follows immediately after (when the low-timing rich mixture finally reaches the o2 sensors)

[2016SSlt1]

stft max 2.png The timing doesn't seem to drop in this instance but it does seem like it starts to go into DFCO then the fuel trims max. I just don't understand why.

[CaudleDynamicsLLC]

Yeah, in pannetrons log the timing drops but dont see that in yours. There are definitely some things still hidden in the ECM for DFCO that HPT isn't accessing/displaying - usually the problem in GenIV ECM's, which I have battled with extensively, is that DFCO only comes on when it feels like it even though all the enable parameters are met.

As far as yours; has the VVE and MAF tuning been done pretty thoroughly down to and below the RPM and load ranges where the issue is occurring, or at least extrapolated down below it reasonably? If, when the RPM drops, it falls into a load/rpm window that wasn't captured by normal driving and VVE/MAF tuning it may be getting tripped up. The actual log file and tune may help get more input

[pannetron]

To be clear (or maybe to further muddy the waters!) the log I posted earlier showed my ECU NOT in DFCO. I just checked that same log and when in DFCO, the "Commanded AFR" stays at 14.68 but my WBO2 goes max lean, around 22+ AFR, still in fuel trim cell 15, timing drops to +15 and shows NOT in closed loop. Saying the Gen IV ECU plays magic in DFCO is an understatement!