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Hello!

Since I'm new here and still getting used to the forum, I'd like to wish everyone a pleasant evening and also mention that I find the posts very interesting.
Then I would like to say something about that one post concerning the AFN Passat and the loss of power (assuming the problem hasn't been resolved yet).
It's possible that a significant amount of oil has accumulated in the intercooler piping, and this oil may also be depositing on the intake air temperature sensor. This can distort the readings. Unfortunately, the control unit doesn't store this error. I would suggest removing the sensor and cleaning it, then taking the car for a test drive. I had the same problem.

Hi, welcome.

Holli33 wrote:

.... Then I would like to say something about that one post concerning the AFN Passat and the loss of power (assuming the problem hasn't been resolved yet). It is possible that a thicker layer of oil has accumulated in the intake air duct, which may also deposit on the temperature sensor for intake air temperature. This will distort the readings. Unfortunately, the control unit does not store this error. I would suggest removing the sensor and cleaning it, then taking it for a test drive. I had the same problem.

The temperature sensor is completely indifferent to the small amount of oil. If it's a combined pressure/temperature sensor, it's not the temperature sensor (the plastic part) that needs cleaning, but rather the tiny opening of the pressure sensor located next to it.
However, it's questionable whether oil sludge significantly affects the readings... it's better to simply measure the boost pressure beforehand.

Best regards, Rainer.

Regarding the temperature sensor/pressure gauge. As I said, I had this problem too. Ultimately, we removed the entire intercooler and drained the oil that had accumulated over time. I also found that cleaning it doesn't last long. But even after extensive searching (using V.A.G. diagnostic equipment and consulting a trusted service technician), nothing else could be found. The problem recurs at irregular intervals, and unfortunately, this has happened with three AFN Golfs so far. I've also considered whether it would be advisable to install a different intercooler. Since I have to drive a lot of highway miles, I thought it might be better for the engine if the air it 'breathes' contains more oxygen, which should also affect fuel consumption. Does anyone know how I can determine/calculate the optimal size of an intercooler? And would it make a difference if I used aluminum pipes instead of the original ones? Oh, and here are the vehicle details: Golf III, year of manufacture: 'V', AFN engine, 5-speed transmission, air conditioning.

Holli33 wrote:

Because of the temperature sensor/pressure gauge. As I said, I also had this problem. Ultimately, we completely removed the intercooler and initially drained the oil that had accumulated over time.

There's probably something else broken there; nothing should be floating in it.

Quote:

I've also noticed that the improvement in cleaning isn't long-lasting. However, even after extensive searching (using V.A.G. diagnostic equipment and with the help of a trusted service technician), nothing further could be found. The problem recurs at irregular intervals, and unfortunately, this has happened with three AFN Golfs now. I've also considered whether it would be advisable to install a different air filter. Since I frequently drive on highways, I thought that it might be better for the engine if the air "fed" into it contained more oxygen, which should also affect fuel consumption. Does anyone know how I can determine/calculate the optimal size of an air filter? And would it make a difference if I used aluminum pipes instead of the original ones? Oh, and here are the vehicle details: Golf III, manufactured in year "V", AFN engine, 5-speed transmission, with air conditioning.

Why don't you first measure the intake air temperature at your preferred highway speed?
Regarding fuel efficiency: a diesel engine operates with an excess of air, even at full throttle, so there shouldn't be significant noticeable differences.
If you install an oversized intercooler: great, instead of a charge air temperature of 40°C (at which point you're already exceeding 160 km/h), you'll have a charge air temperature of 35°C at an outside temperature of 20°C.
Does your car consume significantly less fuel at an air temperature of 15°C compared to 20°C?
If not, then forget that idea immediately.

Regarding your problem with the incorrect intake air temperature readings: please refrain from posting such nonsense as a "start post"; it doesn't come across well at all.

Best regards, Rainer.

Thank you for the quick and easy-to-understand response to my inquiry!
And for the second part: I understand.

Rainer K. wrote:

Regarding your problem with the inaccurate intake air temperature readings: please do not post such nonsense here; that is not an appropriate way to start a thread.

Hi Rainer,

I know that a lot of nonsense is sometimes written here.
But I also believe that it's difficult to seriously criticize some of the authors when they feature stories about people who should actually "know about such things," or convincingly create the impression that they do.

Holli at least mentioned a

Quote:

service technician I trust

.
And those who do not yet have the specialized knowledge to recognize statements from such people as false - one should initially show some understanding towards .

Hi Ulf,

ulf wrote:

And those who do not yet have the specialized knowledge to recognize statements from such people as false - one should initially show some understanding towards them

.
You are right, but imagine if everyone posted something they once heard. I could also write a lot.
Then we end up exactly at "ass-speed" or "sex meeting" websites. I don't want that, so I'd rather just pull the emergency brake immediately.
Also, I don't want any discussions about catalytic converter replacement pipes, as everything is already stated in the terms of service, but some people just aren't interested. }

Best regards, Rainer.

I don't think the 'oil slick theory' is entirely far-fetched.

The temperature sensor might still find it relatively cold, but what about the pressure sensor?

Okay, I haven't actually looked at it yet (and I won't be installing it anytime soon, given the crazy location they want to put it in), but I'm not unfamiliar with this issue from my experience in the machine tool sector.
Sometimes, there can be amazing effects resulting from completely overwhelmed sensory perception.

Considering the whole picture would certainly not be a mistake, in my opinion (for example, measuring the boost pressure and its behavior compared to target values).

CU Gremlin.