Symptoms like missfire, but it is not...

[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 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??

[Alvin]

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.

[Cringer]

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 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??

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

[Leckan]

Ahhh.... Thanks for this info!!

[blindsquirrel]

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.

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