Symptoms like missfire, but it is not...

Hi, Running a L77 with a mild cam, E38, cool air intake and in SD mode only (MAF disabled).

I have this annoying issue that I cannot figure out what is causing it :banghead: It feels like a Miss-fire on ALL cylinders when driving but no DTC is set at all (had real Miss-fire before so DTC is working), it happens very seldom but last time when driving I caught 2 occasions of this "jerk":

11.12.675 & 13.07.963 min into the log file both Cylinder Air and Instantaneous Fuel zeros out for ~100ms, then coming back to normal again. Physical sensor values seems OK (MAP, MAF, Temp, E38 Voltage etc). The car jerked big time and then continued as nothing happened.
20.24.846 & 20.32.503 min into the log file I have the opposite behavioral, fuel and air goes way high for ~100ms without any obvious reason.. Cannot recall noticing this when I drove however...

Been studying the logs back and forth and the only thing I can think of causing this jerking is a SW bug, Watchdog timeout or other SW based issue in the E38 but I can be wrong.. Any other that has experienced similar behavioral or has a clue what it could be??

Yes, I've been calling this the "VVE bug" if you want to search about it. It's the MAP^2 overflowing. You can calculate the VVE table without MAP2 but you won't get the curve in each zone vs MAP.

The easiest fix if available is to apply the 2 bar OS and rescale the tables for 1 bar operation.

Quote:

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Originally Posted by Leckan

Hi, Running a L77 with a mild cam, E38, cool air intake and in SD mode only (MAF disabled).

I have this annoying issue that I cannot figure out what is causing it :banghead: It feels like a Miss-fire on ALL cylinders when driving but no DTC is set at all (had real Miss-fire before so DTC is working), it happens very seldom but last time when driving I caught 2 occasions of this "jerk":

11.12.675 & 13.07.963 min into the log file both Cylinder Air and Instantaneous Fuel zeros out for ~100ms, then coming back to normal again. Physical sensor values seems OK (MAP, MAF, Temp, E38 Voltage etc). The car jerked big time and then continued as nothing happened.
20.24.846 & 20.32.503 min into the log file I have the opposite behavioral, fuel and air goes way high for ~100ms without any obvious reason.. Cannot recall noticing this when I drove however...

Been studying the logs back and forth and the only thing I can think of causing this jerking is a SW bug, Watchdog timeout or other SW based issue in the E38 but I can be wrong.. Any other that has experienced similar behavioral or has a clue what it could be??

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Lots of info here:
https://forum.hptuners.com/showthrea...ittent-Stumble

And here:
https://youtu.be/cRxVVFGRL7A

When the MAP^2 Coefficient is corrupted it will swing the VVE airflow to either Max or Min and your fuel injectors will also be 0% or 100% duty cycle. 2 Bar Custom OS is your best bet. However, if that is not available I recently released Verlon Mode to the public and you now have a work around. You will need to watch the other videos on my VVE Assistant tool to understand what is going on. There is a learning curve, however, this is the most recent demo for this specific instance:
https://youtu.be/T-j7X7xFVss

Ahhh.... Thanks for this info!! :worship:

Quote:

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Originally Posted by Francisnchard

Hello,
Given the behavior of air and fuel "zeroing out" and then returning to normal, it could be due to poor grounding or an electrical fault. If there?s a grounding issue in the wiring harness, it could cause a brief loss of signal, leading to the jerking you're experiencing. Therefore, you can try to check the following two factors:
-Check all grounds related to the ECM, especially if you have any custom wiring for the cam swap or mods. Make sure they are secure and have a solid connection.
-Inspect the battery voltage in your logs and ensure that the voltage isn't dipping during these events.

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No. Ask your chatbot partner which circuit could cause the given behavior.