AFN Engine Problems: Troubleshooting & Repair

Hello everyone.

I am experiencing several issues with the automatic transmission in my A4.

1. A warm engine starts very poorly, or not at all.
2. The engine occasionally loses power and stutters.


Sure, here is the translation of the text from German to English:

"To 1:"

The engine starts easily and without problems when cold, but when it's hot, it cranks endlessly. I've noticed that the mass airflow sensor (MAF) reading is already at 1285g when the engine is idling, and then drops to around 300g when cranking. Is this normal? I thought it should be at zero when idling. It's getting diesel, but it's not starting.

Regarding point 2.

He has the infamous error code 00575. I think it's the N75 sensor. There's virtually no boost pressure. When I control the VTG with a constant vacuum, I get a boost pressure of about 1.3 bar. So, I think the turbocharger itself is okay.

Does anyone have a tip for me, especially regarding error 1? I had to stop searching for error 2 today because it kept overheating and I had to let it cool down before restarting.

Best regards,
Volker

Have you ever replaced a coolant temperature sensor?

Hi, regarding point 1: Check the fuel injection pump for proper operation, and look for any leaks or air in the system.
"2: Check boost pressure while driving, and check the mass airflow sensor (MAF) value."

Hi.

Just search for "warm start problem" and you'll find plenty of reading material.

Good night, Lorenz.

Good morning.

First of all, thank you for the quick responses.
The coolant sensor for the control unit is something I also considered, but it didn't yield any results.
I still need to double-check the funding start date.

What still surprises me is the issue with the amount of air flowing without the engine running. Shouldn't that amount of air be zero?
I'll check right away to see if it starts again. Yesterday, I didn't feel like going all the way to the car.

Hi,

I once had the same problem with the AFN. All diagnostic attempts were unsuccessful.
Letztendlich war es der Anlasser - es gibt da einiges drüber im Netz. Certain.
As models get older, they don't reach their full potential, and that's only natural.
when the engine is warm. It also doesn't matter if the battery is fully charged.

I once stood in the shade in Spain, where the temperature was 40°C, and the engine simply refused to start.
anspringen. Erst nach 2 Stunden abkühlen funktionierte es wieder. At home, then with...
I replaced the Ih-Bäh part, and after the installation, the problem never occurred again .

Hi,

I once had the same problem with the AFN. All diagnostic attempts were unsuccessful.
Letztendlich war es der Anlasser - es gibt da einiges drüber im Netz. Certain.
As models get older, they don't reach their full potential, and that's only natural.
when the engine is warm. It also doesn't matter if the battery is fully charged.

I once stood in the shade in Spain, where the temperature was 40°C, and the engine simply refused to start.
anspringen. Erst nach 2 Stunden abkühlen funktionierte es wieder. At home, then with...
I replaced the Ih-Bäh part, and after the installation, the problem never occurred again .

The BKD engine (which I have in my Touran) is also 'famous' for its cold start problems. I've also experienced these problems, but so far, it's always managed to start.
A potential source of error in the BKD engine is the insufficient speed of the starter motor, which can be caused by its age.

The starter motor is turning it over at about 400 RPM, which I think should be enough for it to start. What's strange is that the amount of air entering the engine at idle is significantly higher than it should be.

Should be 265mg, but it's 385mg.
The start of boost will be at the lower limit. I'll adjust it forward tomorrow and then focus on the problem with the boost pressure.

If it's the first one, I would still replace the starter.

'With my first Ibiza TDI AFN, I experienced the same problem: endless cranking, the starter motor was replaced, and the issue was resolved.'
I just replaced the starter motor in my current Ibiza ASV this weekend, and it starts perfectly both cold and warm. I also noticed that it was cranking for a longer time, so it needed to be replaced before winter.

Both were used starters, described as 'like new,' purchased from an online marketplace, original VAG parts, and each costing around 25 euros.

I've had bad experiences with replacement parts from the aftermarket, as the starting performance didn't improve. It's better to use an original 12V, 2kW starter. For the AFN engine, the 'newer' 024 starter also fits.

If it doesn't start, try unplugging the temperature sensor.
and then start.
If it starts immediately, it's due to an unfortunate combination of...
Starter motors and MSTG software.
With engines that operate at varying speeds, Driss applied a coating so that, as the coolant temperature increases...
more revolutions per minute (RPM) need to be achieved by the starter motor before fuel is injected.
is injected (see image).

Best regards,
Micha