Engine Jerking 1500-2000 RPM, BMW

Hello everyone.

I recently got VCDS, and I'm still a beginner. It's really great software, and the forum has been very helpful so far.

Okay, here's the translation:

Now, regarding the problem... Skoda Octavia RS 2.0 TDi DPF, engine code: BMN, year of manufacture: 2006.

"After a severe coolant loss, a crack was found in the cylinder head and it was replaced. After replacing the head, the engine exhibits severe misfiring when it's warm (approximately above 90°C coolant temperature). Unfortunately, the error memory is empty..."

The following parts have already been inspected, found to be in good condition, or have been replaced...
- LMM (tested with a different LMM).
- Differential pressure sensor (renewed and calibrated).
- PDE wiring renewed.

Here are two more measurement runs (one with a cold engine, one with a warm engine). The fluctuations in RPM are very noticeable in these runs.

"Does anyone have any suggestions on where I should look next? If you need any other values, I'm happy to measure them."

Thank you very much for your help.

Is there any in it?

"Based on my gut feeling, some of those values seem 'Spanish' to me."

Hello, thank you for the reply.

Unfortunately, everything is original.

I also think the values look very strange.

Soll ich noch weitere MWB messen? If so, which ones?

Best regards,

Hi,

"So, an injection amount of 67.5mg/cycle at 1770rpm seems very strange to me, and I also find the target lambda value in the lower RPM range to be too high. I'll take a look at the data set to see what it says."

Best regards, Rainer.

That would be really nice...

Could the problem be related to the vacuum system? It's strange that the issues only occur when the engine is fully warmed up.

Hello,

I need to correct myself; the values actually seem quite standard, although perhaps a bit optimistic considering the hardware (charger) used.

Please log the following measurement blocks for the error case.
- MWB 1, 3, 8, and then again in a separate log.
- MWB 1, 11

Vacuum system: A crack in the vacuum membrane of the diverter valve on the loader could potentially cause this type of error, although it is unlikely.

Best regards, Rainer.

Hello Rainer,

Thank you for your support.

Today, I ran two more tests, but one of the logs looks a bit strange. What I noticed today is that it doesn't seem to be stuttering as much as before. Perhaps it wasn't as hot as usual, but I couldn't get the cooling temperature to increase properly.

Thank you for your efforts... Best regards.

Hello,

In the "2nd login" file, "20110307_1-3-8-WARM2.CSV", it can be seen that the limit related to air mass falls within the range for gear torque.
At the same time, in the file 20110307_1-11-WARM2.CSV, the charging pressure is actually always a bit too low.

Consequently, the turbocharger pressure and fuel injection volume will occasionally fail.

If I were in your position, I would focus the troubleshooting on the vacuum hoses and the VTG (Variable Turbine Geometry) control unit.

Best regards, Rainer.

Hello Rainer,

Thank you again for your support.

I have partially disassembled and inspected the vacuum hoses and the VTG (Variable Turbine Geometry) adjustment mechanism. Unfortunately, I haven't found anything that seems to be incorrect or out of place.

Well, the problem hasn't occurred since the outdoor temperatures have been warmer. I can barely get the coolant temperature up to 97° (that's usually when the jerking started).

I have no idea if everything is okay now. I'll be testing it more thoroughly over the next few days. It can't just disappear like that...

Best regards,
Marcel.

Okay, I have a small update to report.

I've noticed that the engine starts to stutter only when the coolant temperature exceeds 97°C. What's strange is that the instrument cluster only shows a maximum of 90°C. Which signal is used to control the radiator fan? Or am I completely on the wrong track?

best regards, marcel

My AI never shows temperatures above 90°C during normal operation.


The signal for the MSG (Message) and KI (Key Input) originates from the G62 sensor, which should be located on the ZK (presumably a specific component or location).
They sometimes break, but they are not expensive.

At the output of the cooler, there is the G83 chip, which, to my knowledge, only controls the cooler fans.

p.s. How do you know that the problem only occurs at temperatures above 97°?
From the log files?

After numerous test drives using the diagnostic tester, I noticed that the problem only occurs above 97° (according to the diagnostic tester). Once the coolant temperature reaches around 95° (according to the diagnostic device), I believe the jerking/hesitation disappears and is no longer noticeable. However, the instrument cluster always displays 90°.

The difference of 7°-13° (diagnostic tester) compared to the AI (artificial intelligence) is certainly not normal. I thought the sensor only had two connections, or am I mistaken?

You mean I should replace the sensor?

Sorry, I just checked my logs and saw that the problem also occurred at lower coolant temperatures.