Golf 4 TDI jerks/shudders

Hello!

I'm having a problem with a 2001 Volkswagen Golf 4 TDI ALH.

The engine is misfiring at idle when the air conditioning compressor is turned on (when the engine is cold).
"Engine speed fluctuations between 900 and 1000 RPM, and short puffs of smoke. When I switch to ECON mode, the engine runs smoothly immediately, without any misfires. I also felt a brief jerkiness at around 2000 RPM while driving."

When the engine is warm and the air conditioning is turned on, it runs normally.

Best, Chris.

Hello,

Based on my gut feeling, I would say the climate control compressor is faulty or seizing up. However, this doesn't match the smooth running experienced with a warm engine.

What does the idle speed control (MWB13) do? Belt drive quiet, tensioner okay?

Best regards, Rainer.

HI

Mwb 13, all values are approximately 0.

The timing belt and pulleys are all new, and the V-belts and pulleys also look to be in good condition.

I've just updated the Difi software; let's see if it improves things.

The error was due to the mass airflow sensor; it appears that the wrong part was installed, Mr. Metzger.
With the correct Bosch mass airflow sensor, the problem has disappeared.

Best, Chris.

Thank you for the feedback! Background information: If the mass airflow sensor (MAF) readings are incorrect, it's possible that the exhaust gas recirculation (EGR) rate enters ranges that are not intended during load changes (e.g., when the air conditioning compressor is turned on). At some point, the EGR rate becomes too high, and the engine doesn't receive enough fresh air.

-> The LMM (lambda measurement module) values in module 3 of the engine control unit showed anomalies.

Best regards, Rainer.

Hello!

I've now installed the new LMM (likely referring to a Lambda Multi-Point sensor), and now I'm getting an error message.

17552 LMM - Short circuit to ground.

LMM value remains constant at 550.

With the initial settings, no change was detectable. However, this error was not present with the second, incorrect mass airflow sensor (MAF).

I had the same problem with the very first one.

Does anyone have any ideas about buying another one?

Best regards, Chris.

Solution:

Broken wire in the connector of the mass airflow sensor (MAF sensor), pin 4. No 5V present.