ASU Failure: Questions and Answers

Hello community.

I was wondering what could cause an extremely high reading in an emissions test.
I drive a BKD engine with 103 kW, and it doesn't have a DPF (diesel particulate filter). I've been having problems with it for quite some time, but I can't seem to find the source of the issue.

The car is a June 2006 model and had problems during the second-to-last inspection. It failed the initial technical inspection at the local TÜV station, which is why I went to , who then had the inspection carried out again.
The mechanic returned with the inspection report and said, "Everything is fine. He passed without any problems..."

Back then, I didn't think much of it...probably too many short trips, or a measurement error.

Unfortunately, the same problem occurred during the last inspection. This value (is it called the K-value, turbidity value, or lambda value?) was again 20 to 30 times outside of the acceptable range. And this happened even though I had just recently replaced the oil and air/diesel filters.

Unfortunately, no one could immediately tell me what it might be related to. What's the problem? What could be broken or malfunctioning?
There are no error codes registered in the OBD system. The mass airflow sensor (MAF), EGR valve, and tandem pump were recently replaced, and all hoses are in good condition.
As I mentioned, I've been having a problem for quite some time where my car is consuming about 2-3 liters more diesel than it used to.
"I drove for a period of 15 months with a fuel consumption of 7-8 liters (70% city driving). After that, the consumption increased by half a liter every 20,000 km, and I'm currently at 9-11 liters."

The most noticeable thing is when I start driving in the morning with a cold engine, the average fuel consumption reading jumps to between 17 and 20 liters.
I didn't document it, but I remember that the car used to show a fuel consumption of around 11-13 liters on the onboard computer.
I don't know if there's a connection, but this information might be important.

If anyone had an idea, I would be deeply grateful, because I am now at my wit's end, and it has become a matter of honor to solve the problem .
I don't just want to hand the car over to mechanics from the Volkswagen Group and let them search it, as I've had bad experiences in the past.
At least, the ones I know aren't the brightest or most engaged.

Best regards,

In my opinion, the most likely causes for this issue in this engine are:
- Leak in the charge air system, i.e., a hose, connection(s), or intercooler is leaking.
- Faulty electric throttle valve/EGR module.

It's best to try using these keywords in the search function.

Best regards, Rainer.

Off-topic.

If the car is from 2006, why isn't this your first vehicle inspection (AU)?
You are writing in the second-to-last comment.
Don't you have to wait three years before a new car needs its first inspection (TÜV)?
No offense, I just want to understand.

Offtopic off.

@bakkano
It's a taxi, so it has to undergo the annual technical inspection (TÜV) and emissions test (AU).

@rainer

How can I tell if the intercooler has a leak? The hoses should all be okay.
The EGR unit has already been replaced once. First, the EGR valve was replaced because the membrane was slightly leaky, and then the magnetic valve block, which also controls the EGR cooling, was replaced.
Is there any other part that is important for the AGR?

Regards,

Serdar.

serdarg wrote:

@bakkano It's a taxi, so it has to undergo the annual technical inspection (TÜV) and emissions test (AU). @rainer How can I tell if the intercooler has a leak? The hoses should all be okay. The EGR unit has already been replaced once. First, the EGR valve itself was replaced because the membrane was slightly leaking. Then, the magnetic valve block, which also controls the EGR cooling, was replaced as well. Is there any other part that is important for the AGR? Regards, Serdar

Leaks in the charge air system on the pressure side are always indicated by fine oil mist with dust adhering to it, typically found directly at connection points or defective areas, such as a crack in the intercooler. At connection points, I would always compare it to other connection points to assess whether there is an excessive amount. An intercooler should only show oil mist at the connection points; if it's visible directly on the intercooler body, a defect is likely. In that case, you can still try to seal individual areas or replace sealing rings at the connection points.

Best regards,

To rule that out, have you made any modifications to your engine? Like a chip tuning, OBD modification, or an aftermarket control unit, or anything else?

Hi,

So, no modifications whatsoever. Everything is stock. It's a 2.0 TDI engine, BKD, with 140 horsepower.
If the coolant leak was significant, wouldn't it be audible? Or not necessarily?

I already asked a well-known independent workshop, but they said that a leaking coolant pump would sound almost the same as a cracked air hose. And only a VW/Audi (VAG) workshop has the equipment to measure whether the pressure remains the same after passing through the radiator.
"But I don't hear any hissing at all. Or maybe the engine gets so loud at certain speeds that I can't hear any potential hissing."

A few weeks ago, the car was on a lift, and I was inside it while someone accelerated it in gear. During that process, whenever the accelerator pedal was released, there was always a hissing sound coming from the area of the vacuum actuator on the turbocharger itself.
Does that mean anything? Well, if you want to find a mistake, sometimes you start by identifying every possible source, even the most trivial ones, as potential causes .

As I said, the coolant lines and hoses should be sealed, as there's no hissing sound and no signs of contamination on the pipes or connections. Regarding the EGR system, the valve and also the...
New magnetic valve block, which also controls the EGR cooler valve.
Was könnte es noch sein? Furthermore?

Best regards,

If everything is in good working order before the emissions test, accelerate to full throttle several times (around 15 times) on the highway at speeds between 2000-4500 RPM to clear carbon deposits from the exhaust system, and then immediately proceed with the emissions test.

Is there visible smoke when accelerating at full throttle? Or did the inspector accidentally enter the wrong engine code (MKB) for a vehicle with a diesel particulate filter (DPF) into the emissions testing device?

The value is not 2-3 times higher, but 30 times higher than the tolerated level .
I don't think it has to do with the exhaust... I actually sometimes let the exhaust out. Taxis, after all, don't just operate in city traffic .
I don't think it's related to the mainboard either. Something must be broken, but unfortunately, I can't figure out what it is using my own logic.
No error message, no hissing sound.

If the intake manifold gasket were leaking, wouldn't that register as an error code, such as a vacuum leak or similar issue?


Best regards,

It should actually be sealed... but it hasn't been checked .

I have an appointment at the VAG workshop on Tuesday. Let's see what they find . I will report back.

Best regards,

serdarg wrote:

The value is not 2-3 times higher, but 30 times higher than what is tolerated . I don't think it has to do with the exhaust... I actually sometimes let the exhaust out. Taxis, after all, don't just operate in city traffic . I don't think it's related to the mainboard either. Something must be broken, but unfortunately, I can't figure out what it is using my own logic. No error message, no hissing sound. If the intake manifold gasket were leaking, wouldn't that register as an error code, such as a vacuum leak or similar issue? Regards

.

30 times higher That would require seeing a lot of Russian... Errors occur when the LD is over or undershot!
With mini-Lex systems, for example, errors can occur during high-speed operation without load because there is insufficient intake air and exhaust gas mass to allow the turbocharger to function correctly.

What is the air mass and lambda (LD) at full load in gears 3-4 at 1500-4500 RPM? Can you see any signs of Russ during acceleration? If so, from what RPM, air mass, and LD values? Could it be a faulty catalytic converter? Compare the exhaust flow by hand with other 1.9L TDI engines at low load. Also, try temporarily disabling the EGR valve for testing.

T3Surfer wrote:

The value is not 2-3 times higher, but 30 times higher than the tolerated level serdarg wrote: . I don't think it has to do with the exhaust... I actually do that sometimes. Taxis, of course, don't just operate in city traffic . I don't think it's related to the mainboard either. Something must be broken, but unfortunately, I can't figure out what it is using my own logic. No error message, no hissing sound. If the intake manifold gasket were leaking, wouldn't that register as an error code, such as a vacuum leak or similar issue? Regards;). 30 times higher That would require seeing a lot of Russian... Errors occur when the LD is over or undershot! With mini-Lex systems, for example, errors can occur during high-speed operation without load because there is insufficient intake air and exhaust gas mass to allow the turbocharger to function properly. What is the air mass and lambda (LD) at full load in gears 3-4 at 1500-4500 RPM? Can you see Russ during acceleration? If so, from what RPM, air mass, and LD? Could it be the catalytic converter? Compare the exhaust flow by hand with other 1.9L TDI engines at low load. Also, try temporarily disabling the EGR valve. Yes, approximately 30 times higher. I cannot observe the Russian engine myself. When running at full throttle, it tends to emit a whitish, slightly bluish smoke. I can't say that it produces black soot. I need to measure the air mass and LD (likely referring to a specific sensor or value). It's clear that when I accelerate with full throttle from low RPM, the car goes into limp mode. The error message then reads: "Boost pressure control exceeds regulation limit." Sometimes with a "Sporadically" after it, and sometimes just "--". Anyway, the car feels like there's a rubber band attached to the back, and it tries to pull itself back. Especially when there are 3 or 4 people inside, it struggles significantly at low RPMs, sounds like a truck, and is also very loud. Comparable to someone with a heart condition who has to climb three floors

.

Okay, so the car is going to the workshop on Tuesday. I've asked them to fix the problem, and primarily they should check the intercooler/turbocharger and verify the timing belt settings.
Grobe Zahnversätze kann es beim PD ja nicht geben, wie ich immer wieder höre. Aber irgendeine Feineinstellung wird es doch da geben? Steuerzeiten,dyn. Ffunding start, etc.
What could be wrong with the timing belt on a 2.0 TDI engine if it's impossible for it to be off by just one or two teeth?

Something must be wrong...
Yes, it is possible to make mistakes when working on the timing chain. The camshaft sprocket is adjustable. It must be precisely aligned using either the crankshaft locking tool or the camshaft alignment mark, along with the camshaft lock or a similar device. A 3-degree adjustment can have an effect! I cannot imagine adjusting it by a whole tooth, because if you move it by two teeth, the valves could collide with the pistons.

How do you know your car has too little exhaust mass? Just because the lambda value is low? The sluggish acceleration from low RPM can also be explained by the insufficient lambda value! Have you already checked the exhaust pulses at the end of the exhaust pipe by hand, comparing it to other similar 2.0 TDI engines? Perhaps the catalytic converter is clogged!

Okay, I'm curious to see if Volkswagen will manage to fix it correctly, or if they'll completely mess it up by replacing unnecessary parts, or if they'll use a different part for the same purpose.

It's sad that many "MASTER" technicians have less knowledge than a deaf "simple" mechanic like me, and yet they act so superior that I feel inferior.

I'm also going to have the catalytic converter checked. Yesterday I noticed that when you give it gas at idle, almost no exhaust comes out. Only when the car is cold does it produce a lot of white smoke, and when you floor it at night, you can see a grayish-blue haze more clearly in the light from the vehicle behind you.
Otherwise, very little comes out of the exhaust pipe; you could almost say nothing at all.
And if you hold your hand in front of it, you can feel the pulsating bursts of gas.

I just don't understand the logic. If it were possible for a cat to be inside, where would all the exhaust go? It has to escape somewhere, right?

The exhaust gases are slowly escaping through the clogged catalytic converter, which you can tell by the minimal or nonexistent pulsing felt on the exhaust pipe when touched. I'm asking again: have you ever compared it to other cars with similar engines? That's the only way to get a good comparison! You could also remove the catalytic converter and drive around without it for a while! It's not that loud on a TDI!