Decel RICH condition?

I have an LS3, E38, cam, heads, converter, etc...all N/A on pump gas...

When I am cruising at highway speeds and cut the throttle back to idle and coast down, I noticed the wideband gauge reads .85. Strange I thought. So when I look at the logs. I see that indeed wideband shows rich, and the narrowbands agree since the voltage is high/rich (850 mV). Yet the STFT + LTFT is showing +32%! I cannot understand the ECU would keep dumping in fuel when the O2's are reading rich. And this rich condition may last 10-20 seconds during a coastdown too.

COT is disabled
DOD is disabled
DFCO is disabled
Desoot is disabled

I have checked and resealed for exhaust leaks and didn't see any changes. I guess I will try to disable LTFT and see if that changes anything. But other than that I am out of ideas.

Attachment 118055
https://imgur.com/a/QaUw0dI

I have the exact opposite problem. Mine goes 1.25 lean on hard decel. I'm open loop all the time also (intentional) so I have no O2 or fuel trims in the mix.

On a whim I decided to disable LTFT and that fixed the problem. Not sure how that's the issue though...unless it need more learning time?

I've never used closed loop.

That said, even in open loop with DFCO working properly, on a decel my wideband showing -.- too lean to read,

I can still smell fuel going through it. Scanner shows 0.6% Injector duty during DFCO decel.
I even put 0's on the top row of the VE table to help cut the fuel.


Seems like no matter what we do, a little fuel still goes in. Shame. But curious, why? Injector driver wont shut up?
I'm toying with an idea to use arduino to cut power to the injector supply during decel using TPS and RPM/MPH as a trigger. But so much work... I wonder how much fuel I would save if any.

Quote:

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Originally Posted by Cringer

On a whim I decided to disable LTFT and that fixed the problem. Not sure how that's the issue though...unless it need more learning time?

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I have my LTFT disabled and my STFT?s still shoot up to 32% during decel when DFCO is not active. E92 pcm, i dunno what the solution is other than to have DFCO on at all times during no throttle.

Give this a try, had the same issue and couldn't figure out why the trims would command rich on decel and then also dfco would not kick in in 5th and 6th only 4th and down. Found this fix on here made these changes and now dfco works all around.

Engine
-> Fuel
--> open and closed loop
---> Ltft idle cells thresholds

Set enable vss to 255
Set disable vss to 256

Quote:

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Originally Posted by brewster

Give this a try, had the same issue and couldn't figure out why the trims would command rich on decel and then also dfco would not kick in in 5th and 6th only 4th and down. Found this fix on here made these changes and now dfco works all around.

Engine
-> Fuel
--> open and closed loop
---> Ltft idle cells thresholds

Set enable vss to 255
Set disable vss to 256

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Thanks for the suggestion! I will experiment with that once the weather gives me a windows to drag the ol gurl outta the garage!

Quote:

---

Originally Posted by brewster

Give this a try, had the same issue and couldn't figure out why the trims would command rich on decel and then also dfco would not kick in in 5th and 6th only 4th and down. Found this fix on here made these changes and now dfco works all around.

Engine
-> Fuel
--> open and closed loop
---> Ltft idle cells thresholds

Set enable vss to 255
Set disable vss to 256

---

I know it has been a while, but I did want to say thank you, this did work!