Golf V BKC: Analyzing Messwertblock 003 Issues

Hello everyone,

I'm having a small issue with a Golf V, manufactured in 2005, with engine code BKC. The engine has now been driven approximately 67,000 km. For about 1,000 km, it has been performance-tuned to approximately 135 horsepower and 310 Nm of torque.

Problem: For approximately 15,000 km, I've noticed a very strong vibration and jerking when accelerating from low RPMs (around 1600 RPM) to around 2200 RPM. This only occurs under full load. If I accelerate slowly, there's nothing noticeable. Top speed and acceleration above 2200 RPM are fine.

I have now created a log file for measurement block 003. I was using an English version of VCDS.

Question 1: Are the following translations correct?

- Exhaust Gas Recirculation (spec.) mg/stroke -> Target value for exhaust gas recirculation, mg/stroke.
- Exhaust Gas Recirculation (actual). mg/stroke -> Actual value of exhaust gas recirculation, mg/stroke.
- Exhaust Gas Recirculation (EGR) Duty Cycle % -> Setpoint for EGR valve.

Question 2: Does a high percentage value in the valve position indicate an open or closed valve?

Question 3: How is it possible for the actual Exhaust Gas Recirculation (EGR) value (mg/str) to be significantly higher than the specified EGR value (mg/str)?

File in the upload area.

/viewtopic.php?p=147894#147894

Best regards,
Schewisch.

It sounds more like ZMS at first glance.
Neither the AGR (Abgasrückführung) nor the turbocharger are fast enough to be described as "vibrating."

"I'm familiar with the ZMS rattling noise from Passat models with 140 and 170 horsepower TDI engines."
It's also temperature-dependent - of course, a feather is softer in the summer.

m;

hello,

Thank you for the information.

"Hmm, yes, I've also been thinking about that. It's difficult to define a vibration; it could also be a rapid jerking. The error memory is clear except for a faulty glow plug. The jerking was also present before the tuning, but it has been amplified after the tuning."

A colleague (a car mechanic) suggested that a faulty mass airflow sensor (MAF sensor) could potentially cause similar errors. I'm going to replace it tonight and then do another logging session.

Despite everything, I still don't understand the recording of the air mass values. As far as I understand it, a high EGR valve setting should always indicate an open valve. If that's the case, then my EGR system is not working correctly.

bashful

Conceptually, I would describe it like this:

Jitter: low frequency (max 2 Hz), sharp impacts.

A ZMS (presumably referring to a specific type of device or component) operates at a higher frequency and produces a softer sound.

Hello,

Okay, so it's a rubbing sound, not the mass airflow sensor. I tested it by installing a new one, but the symptoms are the same. I did the sliding test on a flat surface, and I can push the Golf forward and backward without any spring effect. There's a slight clicking sound, but the entire engine block seems to lift slightly out of its mount. I need to compare it to another Golf.

What I've also noticed is that when the clutch is "pressed down," there's a slight rattling sound, and occasionally, there's a cracking noise when the car is idling.

The mass airflow sensor (MAF) is now reporting values of around 250mg/stroke at idle.

What other diagnostic data can I log to identify the source of these vibrations, in case they are not of mechanical origin? The rattling noise only occurs starting in the 3rd gear.

bashful

Hello,

I drove again and noted down "MWB 11". The target boost pressure starts to oscillate around 1600 RPM, and so does the control duty cycle. How can this happen? What could be causing the limit to be reached, resulting in this oscillation of the target value?

"viewtopic.php?p=147916#147916"

Could it be due to a jerky VTG (vehicle traction generator)?

While I was checking the engine data on the diagnostic tool (OBD), the mass airflow sensor reading suddenly increased from 250mg/stroke to 450mg/stroke. After a few seconds, I pressed the accelerator, and the reading went back down to 250. This value is usually reached when the EGR valve is stuck, right?

Sure, here's the translation:

"Schewisch" - "Schewisch"

schewisch wrote:

Hello, While I was checking the engine data via the OBD interface, the mass airflow sensor value suddenly increased from 250mg/stroke to 450mg/stroke. After a few seconds, I pressed the accelerator, and the value dropped back to 250. This value is usually reached when the EGR valve is stuck, right? Schewisch

That's normal because after a certain amount of time in "limp mode," the exhaust gas recirculation (EGR) system is deactivated. When you then press the accelerator, it will be reactivated.

Wow, what is that?
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The boost pressure is nicely adjusted to the target value, and then suddenly jumps significantly higher.

Did a toy tuner attempt something like overboost?
A BKC with 2500 mbar is already impressive!!!

For these 2500 mbar, my 170 hp BMR engine has a different turbocharger than the 140 hp version... I would be skeptical about that.

m;

hello,

Hmm, yeah, I'm not really happy with the boost pressure either. The tuner is a small, local shop, but he already chipped my Passat AVF three years ago, and I drove that engine for 210,000 km with the tuning without any problems. That's why I went back to him.

"This is really annoying now, this jerking motion, the boost pressure fluctuating, and it's running too much boost. I think I'll call and have them revert the tuning."

Okay, I just spoke with the tuner. He also thinks that 2500 mbar is too high. I should come by so he can re-flash the factory software, and then I can continue troubleshooting. He suspects the problem is either mechanical (VTG) or a faulty valve (solenoid valve?).

He wouldn't allow more than 2100 mbar. That could be the case, as the boost pressure also influences it, and then it might "run away." From a control engineering perspective, I would say that there's too much integral action involved.

Do you have any other ideas about where the oscillations in the target boost pressure might be coming from? They were already present even without any tuning.

bashful

hello,

I have just reviewed the logs again. When the boost pressure oscillates around the target value, the throttle position is also reduced, which is correct so far. However, the actual boost pressure does not react to this, which suggests that the VTG (Variable Turbine Geometry) is not moving away from the closed position as desired.

At a boost pressure of 2500 mbar, I have a duty cycle of 23%. However, the boost pressure is increasing very slowly. I will try replacing the magnetic valve tomorrow.

Gibt es eine Möglichkeit an das VTG-Gestänge ranzukommen ohne den Motor auszubauen? Meine Arme waren zu kurz, und ich konnte nichst sehen. J"Does anyone have a suggestion?"

edit: The stuttering was caused by the dual-mass flywheel.

bashful