STFT "Lazy" after reflash... Corrupted PCM??

Hey everyone. I've been puzzled with strange, slowly switching STFT for a few months and finally found where the behavior started suddenly after a re-flash about 5 months ago. Sorry if this has already been discussed on the forum but I could not find any related threads.

I've attached the tune/log immediately before the problem, where the STFTs look normal:

Attachment 101056
Attachment 101057

...and the first useful log and tune after the problem appeared:

Attachment 101058
Attachment 101059

You can see the STFTs act much slower.

Here are some potential causes for the weird STFT trends that I think I've ruled out:

1. cam phasing changes - NO, earlier tunes used more correct cam phasing and had normal STFT behavior
2. bad/fouled O2 sensors - sensors were changed since the problem started, but they did not resolve it
3. Adaptives need a hard reset - Battery was disconnected overnight; problem remains
4. logging Settings, polling interval, number of channels... - Run 76 was logged with very few channels just to see if the logged fuel trims would return to normal switching; they did not.

I'm probably going to discuss further with HPT Help Desk and/or Hotwire Auto to see if they can help. Just putting this out here in case you all know of other issues.


Background - This is a 2016 6.4 Hemi in a 2008 Jeep Wrangler, NGC4 PCM, harness and initial PCM setup by Hotwire Auto, manual transmission. Stock Hellcat exhaust manifolds. Here's the most current tune and log with newer O2 sensors. The WB fluctuates normally, but the STFTs are still moving more slowly:

Attachment 101060
Attachment 101061

Those STFTs don't look bad at all. Are you actually experiencing a problem?

Thanks for responding. The STFT in the Run 74 log switch very quickly, about as fast as the O2s are switching. In the later logs, the STFT looks lethargic, switching much slower than the O2s. I think the fuel trims are also correcting too slowly, making the AFR swing more than it used to. For example, when shifting gears, the AFR will go lean, but by the time the fuel trims have responded with more fuel, they seem to overshoot and make AFR go too rich. In earlier runs, the faster fuel trims would often correct so well that there would be no rich or lean spikes.

Quote:

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Originally Posted by rockystock

Thanks for responding. The STFT in the Run 74 log switch very quickly, about as fast as the O2s are switching. In the later logs, the STFT looks lethargic, switching much slower than the O2s. I think the fuel trims are also correcting too slowly, making the AFR swing more than it used to. For example, when shifting gears, the AFR will go lean, but by the time the fuel trims have responded with more fuel, they seem to overshoot and make AFR go too rich. In earlier runs, the faster fuel trims would often correct so well that there would be no rich or lean spikes.

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What you've just described is a feature of the proportional fueling control used to maintain catalyst effectiveness. They must receive alternating rich and lean exhaust gases to keep a proper oxygen loading and minimize emissions. I don't think your log looks problematic at all.

Quote:

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Originally Posted by smokeshow

What you've just described is a feature of the proportional fueling control used to maintain catalyst effectiveness. They must receive alternating rich and lean exhaust gases to keep a proper oxygen loading and minimize emissions. I don't think your log looks problematic at all.

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Hey thanks again for your help. Here's a couple of excerpts from the Run 74 and Run 399 above, with similar operating conditions. In Run 74, the STFT is shown going up and down at about the same speed as the WB AFR, which is what I'd expect because the PCM should be making the AFR oscillate for the cats. BUT, in Run 399, the STFT is shown shifting very slowly, even though the AFR is still going up and down at about the same speed as in Run 74. So I think something happened during an earlier reflash that's somehow corrupted how the fuel trims are either calculated or reported on the bus, or something else.

Attachment 101076
Attachment 101077

Just tying up loose ends...

My problem with the 'lazy fuel trims" was that I was logging too many parameters. Not enough bandwidth for all those pids, so the mpvi2 and/or scanner and budget laptop wasn't getting all the requested data.

Quote:

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Originally Posted by rockystock

Hey thanks again for your help. Here's a couple of excerpts from the Run 74 and Run 399 above, with similar operating conditions. In Run 74, the STFT is shown going up and down at about the same speed as the WB AFR, which is what I'd expect because the PCM should be making the AFR oscillate for the cats. BUT, in Run 399, the STFT is shown shifting very slowly, even though the AFR is still going up and down at about the same speed as in Run 74. So I think something happened during an earlier reflash that's somehow corrupted how the fuel trims are either calculated or reported on the bus, or something else.

Attachment 101076
Attachment 101077

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Just had a quick glance over these and it seems like you are logging a lot LESS parameters when the slow STFTs are occurring?

What polling rate are you requesting for the STFTs?

Quote:

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Originally Posted by HaasExp

Just had a quick glance over these and it seems like you are logging a lot LESS parameters when the slow STFTs are occurring?

What polling rate are you requesting for the STFTs?

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That was over a year ago but yeah thanks for reminding me. I believe I was also messing with my polling rate; I think I had them set too high trying to troubleshoot the problem. So I think the polling rate (for my setup, maybe others) doesn't work well for anything faster than about 100ms / 10Hz.