VAG-COM: Interpreting LMM Values - A Guide

Hello,
I used VAG-COM to check the values for the mass airflow sensor, and I'm a bit confused.
The first display shows the specified value (setpoint?), and the second display shows the actual value.
Both values change with the engine speed, and in my case, they are quite different. For example, at idle, the target value is 240mg/revolution, while the actual value is 440mg/revolution. At high speeds (while stationary), the target value is 800mg/revolution, and the actual value is 600mg/revolution. (All figures are approximate and from memory.)
I installed a new language model, and the old one showed significantly different values, but had a similar structure.

"How should the actual value normally compare to the target value? I'm not sure if my airflow is significantly different from the original... Anyway, it's also smoking in a strange way."

Regards,
Carsten.

Hi CarstenAFN,

The target value simply describes the minimum amount of air that must be available to the engine in order to burn the specified amount of diesel fuel cleanly for the given operating condition. If the actual value is now below the target value,
The engine control unit then reduces the amount of fuel injected accordingly. With further decreasing mass airflow (MAF) sensor readings, a noticeable lack of power will eventually occur. The fact that your actual MAF sensor readings are approximately double the target values at idle or partial load suggests that your EGR valve is either defective or deactivated (which is often the case). By the way, how did you obtain these values? The engine must be at operating temperature, and the measurements should be taken in 3rd gear with full throttle over a wider RPM range. Please let the real experts correct or add to anything further in my post, or feel free to write here.

Normally, how should the actual value compare to the target value? I'm not sure if my air distribution system is working significantly differently than the original. Also, it's producing some strange smoke.


The actual value should follow the target value, with only a minimal deviation.

'I'm a bit confused by your values. Did you modify the EGR valve? If not, how long did the engine idle before the first measurement? Did you change anything related to the air intake? What exactly did you change?'
What kind of vehicle is it? What engine does it have (the 'nick' suggests it might be an AFN, but what's the year of manufacture and the mileage)? Because, the crystal ball is currently out of order...


CU Gremlin.