CFCA T5: Wave-like Driving Behavior

Hello, fellow diesel mechanics...

I have a VW T5 from 2011 with the CFCA engine, 180 horsepower. I bought the car with the information from the previous owner that a local tuning shop had deactivated the AGR valve.

I've now noticed that, especially when using cruise control, the gas is being cut off in a wave-like pattern under partial load. It's as if you're briefly lifting off the accelerator for 1-2 seconds, then it returns to normal. After doing some research here on the forum, I've come to the idea that it might be related to the mass airflow sensor (MAF). Could it be that the tuner didn't adjust the maximum MAF value, and that's causing this phenomenon?
"If so, can I adjust this value using VCDS? The MAF sensor is already new."

Sure, here's the translation:

"Thank you in advance."

Hi,

Theoretically, it could be caused by inaccurate mass airflow sensor readings or inappropriate software modifications in the ECU.
The maximum displayed LMM (mass airflow sensor) target value has no effect on the driving behavior if it remains at its original setting. This value cannot be adjusted via diagnostics; it is a pre-defined map.

Okay, I suspect there might be a corrupted file, but if that's the case, it must have always been that way. Alternatively, it could be a sticking VTG (Variable Turbine Geometry) that causes the boost pressure to rise too high and is difficult to regulate back down.

You can easily check this by comparing the target value and the actual value of the boost pressure in the measurement data.

Best regards, Rainer.

I also checked the VTG (Variable Turbine Geometry) and everything seems to be working smoothly and is properly adjusted, but the previous owner couldn't confirm that. Since I've owned the car, it's been doing this.

As I mentioned, I've already replaced the LMM (mass airflow sensor), the rail pressure sensor, the rail pressure control valve, the vacuum lines, and the boost pressure control valve (N57). The boost pressure control valves are also new.

Quote:

The latter can be easily checked by comparing the target value and the actual value of the charging pressure in the measurement data.

Please check the system under fault conditions, not just when stopped at a red light. Create a log and upload it here.

Hopefully, someone can make use of this. Unfortunately, it hasn't made much of a noticeable difference today. Also, the injector values seem a bit strange to me.

Hello,

"I can't find any relevant information in the log regarding smoke. The turbocharger pressure control also seems to be working correctly. The throttle valve remains open, and the EGR valve is closed. I need to check the measured values to make sure there's nothing wrong with the data set."

The Injector 2 seems to be incontinent.

Please check the rail pressure regulation to ensure it is functioning correctly.
Regarding the injectors, I would measure the return flow rates and then decide how to proceed.

Does the vehicle reach its full power?

Best regards, Rainer.

Okay, I'll drive it again and record the values for the EGR and throttle valve. Checking the injector return flow rates isn't easy because part of the turbocharger piping needs to be disassembled to access the lines for cylinders 1 and 2.
Are there any other ways to identify the malicious injector?


It's hard to say exactly what the power output is, but it feels good. The top speed is approximately 185 km/h on a straight road, and it has good acceleration from around 1600 RPM.

Unfortunately, I only know this car superficially and have no basis for comparison.

Here are the data for the throttle valve and EGR system, as well as additional information and injector values.

Hi,

You say AGR is off, then we don't need any logs, but you need to check if the AGR valve is closed and the throttle valve is open during operation.

"Aus" means "out," and that's that. There's no room for interpretation.

If that's not the case, then the dataset in the ECU is corrupted.

The original dataset would also be legally compliant.

Best regards, Rainer.