ASU Issues: Troubleshooting and Solutions

Hello everyone,

I've been reading here for a while now, but today I need to reach out to you all with a problem. The vehicle is a Passat 35i with engine code 1Z.
Sure, please provide the text you would like me to translate from German to English.
I failed the ASU (presumably a medical examination) spectacularly. The turbidity values are all above 2 /m³ (2.29, 2.29, 2.83).
After reviewing the technical articles and other resources here, I'll take a closer look at the AGR valve tomorrow, check the mass airflow sensor, and replace the air filter.
My questions regarding the topic:

Wie würde sich denn ein defekter KAT bei der Messung bemerkbar machen? Liegen die Trübungswerte dann noch höher oder wär das auch eine Möglichkeit die ich bei den oben genannten Werten in Betracht ziehen müsste?

Mir ist aufgefallen, dass er sich in letzter Zeit recht schwer tut auf Temperatur zu kommen, er schaukelt immer so bei 80 Grad rum. (Der neue Thermostat liegt schon hier) Kann dieses längere "zu kalt" fahren einen Einfluss auf die Abgaswert-Messung haben?

Ich bin heut´ 300km Autobahn gefahren und hab die Gelegenheit genutzt, ihn mal richtig zu treten. (Wurde in einem Thread zum Thema ASU empfohlen). Normalerweise bin ich ned so fix auf der AB unterwegs. v-max erreicht er, er war auch fast auf 90°C und hat geschnurrt wie ein alter Kater. Allerdings hat er dann nach ein paar km zu rucken angefangen. Nie wirlich hart, immer nur drei oder vier mal, hat sich auch recht schnell wieder gelegt, als ob er sich verschluckt hätte. Ist das das berühmte "Dreck wegbrennen" oder hat er da ein anderes ernsthaftes Problem? NI can almost rule out adelhubgeber, because it's too rare and it doesn't really jolt or shake violently.

Okay, those are my issues. I would appreciate it if someone could offer some helpful comments on them. Unfortunately, I can't provide VAGCOM data because I don't have a laptop.

Thank you in advance.

Best regards from Freising.
Christoph.

The jerking or sputtering is more likely not a case of "burning off impurities," but rather the injector driver or needle lift sensor in the third injector.

Could you please post how many kilometers your vehicle has already driven. And whether anything has already been replaced (which would eliminate it from the troubleshooting process).

If it never really reaches its operating temperature, the warm-up phase becomes longer, and consequently, the time during which the engine burns fuel somewhat "incompletely" increases. I can imagine that this might have caused some soot to accumulate in your exhaust system.

And, you should also post about your driving habits, whether you mostly drive short or long distances, whether you use the car frequently (e.g., for work) or only occasionally for personal use.

@faz: In the case of mild jerking, I would not attribute it to the NHG (North Sea Gear). This type of gear typically manifests through more pronounced jolts.

"Soft jolts under full throttle likely indicate air in the system. Are there air bubbles in the clear line leading to the ESP? This could cause the injection advance to be misaligned, affecting the injection timing. Consequently, this leads to incorrect injection timing, poorer combustion, and increased soot. Also, check the diesel filter and ensure the sealing ring on the preheating valve is tight. Additionally, the fuel tank ventilation might be an issue. If the soft jolts are reproducible, try driving without the fuel cap for a while."

AGR is, of course, also a strong candidate. And it is generally advisable to neutralize it using a metal plate.

The thermostat should definitely be replaced, mainly to prevent the engine from running in a cold state all the time (which increases wear and tear...). I don't know if it affects the emissions test. But I certainly wouldn't subject my car to the high RPMs of the emissions test while it's only partially warmed up...

Otherwise, I can think of a few more right away.
- Injector nozzles (have the spray pattern and opening pressure checked).
- Exhaust pipe may be clogged due to conservative driving (should clear after a few kilometers of full throttle).
one.

Does the car visibly emit smoke in the rearview mirror when you, for example, accelerate from 1500 to 4000 RPM in second gear? You might be able to gauge the results yourself before unnecessarily going to the emissions testing station.

Regards,
Sure, here's the translation:

"Guste" is a German word that means "gust" or "gust of wind." It can also be used to describe a sudden burst of something, such as laughter or anger.

Zoidberg wrote:

I can almost rule out the needle jump phenomenon, as it occurs too rarely and the movement isn't really harsh.

...
Before I post here, I should probably wake up properly... sorry for my nonsense .

Morning.

Thanks in advance for the initial responses. The engine now has 285,000 km (approximately 177,000 miles) on it, and as far as I know, nothing major has been replaced. Besides the usual maintenance items like the timing belt, air filter, and fuel filter (I've only owned the car for 30,000 km), nothing else. The driving is mostly long distances, with some city driving in between. I rarely drive it at full throttle, but as I said, yesterday I really pushed it on the A9 highway to Munich – to try to "clear out" a potentially clogged exhaust. And these described "jerks" only started happening after that. Otherwise, it doesn't do that.
And yes - when I accelerate, but only when I suddenly and forcefully press the gas pedal, not during slow acceleration, I can see my exhaust fumes (but only at night in the headlight beam of the car behind me). During the day, nothing is visible.
In what way is the LMM a candidate?

Okay, I'm going to go change the thermostat now.

Thank you very much.
greetings
Christoph.

Zoidberg wrote:

The engine now has 285,000 kilometers (approximately 177,000 miles) on it, and as far as I know, nothing major has been replaced.

"I would start by checking the injectors... it's probably best to replace them all. With that mileage, the spray pattern is likely not what it should be anymore (search term: injector wear part)."

Hi,

Okay, I just wanted to quickly tell you how the story ends:
After installing the new thermostat, driving a few kilometers on the highway, and replacing the air filter, I passed the emissions test today. Although, in my opinion, the opacity value was still quite high (1.3), at least I have my sticker. I will definitely follow the tip about the injectors - however, I don't have any money for a new set right now. But in time, there will be new injectors .
Thank you again for the answers you provided!

until the days.
Chau.
Christoph.