Question: Failure with ASU

Hello community.

I was wondering what could cause an extremely high value in the emissions test.

I have a BKD 103kw, without DPF (which I've been having problems with for some time, and I can't find the problem).

The car is from 2006 and already had problems during the previous MOT. It failed the MOT inspection at the local TÜV, after which I went to the mechanic who re-inspected the car.

The mechanic came back with the inspection report and said: "It's all fine, isn't it? It passed without any problems..."

I didn't think much of it at the time... probably too much short-distance driving, or a measurement error.

Now, the same problem occurred again with the last inspection. This value (is it called the K-value, the Türbung value, or the Lambda value?) was again 20-30 times outside the tolerance. And this was despite the fact that I had the oil and air/diesel filter changed just before.

Unfortunately, no one could immediately tell me what might be causing the problem. What could be the issue?

There are no error codes in the OBD system. The LMM, AGR valve, and temperature sensor were recently replaced. The hoses are also in good condition.

As I mentioned, I've been experiencing this problem for some time now: my car consumes approximately 2-3 liters more diesel than before.

Over a period of 15 months, I've been driving around 7-8 liters per 100km (70% city). After that, the fuel consumption increased by about 0.5 liters every 20,000km, and I'm currently averaging 9-11 liters.

The most noticeable thing is that when I start the engine in the morning, the MFA displays a fuel consumption of 17-20 liters.
While I haven't documented it, I remember that the car used to display a fuel consumption of around 11-13 liters.
I don't know if there's a connection, but the information might be important.

If someone had an idea, I would be incredibly grateful, because I'm currently at my wit's end, and it's become a matter of principle for me to solve this problem.

I also don't want to just hand the car over to VAG mechanics and have them fix it, as I've had bad experiences in the past.

In any case, the people around me aren't the brightest or most engaged.

Best regards

In my opinion, the most likely causes of this engine problem are:
- Leak in the intake system, i.e. hose, connection(s) or air intake cooler leaking.
- Defective electronic throttle valve/AGR module.

It is best to search using these points.

Best regards, Rainer

Off-topic on

If the car is from 2006, why isn't this your first inspection?
You're talking about the second-to-last inspection...
Don't you have to get a new car inspected after 3 years?
I just want to understand.

Off-topic off

@bakkano
It's a taxi, so it needs to be inspected annually at the TÜV/AU.

@rainer
How can I determine if the air-charge cooler is leaking? The hoses should all be okay.
The AGR unit has already been replaced. First, the AGR valve was replaced because the membrane was slightly leaking, and then the magnetic valve block, which also controls the AGR cooling.
Is there another part that is important for the AGR?

Best regards,
Serdar

serdarg hat folgendes geschrieben:

@bakkano It's a taxi, so it needs to be inspected annually at the TÜV/AU. @rainer How can I determine if the air-conditioning condenser is leaking? The hoses should all be okay. The AGR unit has already been replaced. First, the AGR valve was replaced because the membrane was slightly leaking, and then the entire solenoid valve block, which also controls the AGR cooling. Is there another part that is important for the AGR? Best regards, Serdar

Leaks in the air intake system, particularly on the pressure side, are always visible as fine oil mist with dust adhesion directly at connection points or defective areas, such as a crack in the air-to-water cooler. When evaluating connection points, I would always compare them to other connection points to determine if there is excessive leakage. An air-to-water cooler should only show oil mist at the connection points. If it is visible directly on the air-to-water cooler body, a defect is likely. In this case, it may still be possible to try to tighten the individual connections or replace the seals at the connection points.

Greetings

To rule that out: have you made any modifications to your engine? Chip/OBD or box or something else?

Hi,

kein Tuning. Alles Original. 2.0 TDI, BKD 140PS

Wenn der LLK wäre undicht, müsste man das doch hören? Oder nicht unbedingt?

I already asked a local independent workshop, but they said that a non-optimized LLK (likely referring to a coolant leak detection system) would sound almost exactly like a leaky air hose. And only a VAG (Volkswagen Audi Group) workshop would have the tools to measure whether the incoming pressure actually exits the system after passing through the radiator.

However, I'm not hearing any hissing. Or the engine gets so loud at certain RPMs that I can't hear any hissing.

A few weeks ago, the car was on the stage and I was sitting inside, accelerating through the gears. When I released the gas, there was always a hissing sound coming from the vacuum line on the turbocharger itself.

Does this indicate a problem? Well, if you're trying to find a fault, sometimes you start identifying even the slightest noise as the source :)

As I mentioned, the EGR system should be functioning correctly, with no hissing and no contamination in the pipes and connections. The EGR valve housing and the solenoid valve block, where the EGR cooler valve is also controlled, have been replaced.

What else could it be? Also?

If everything is IO, before the inspection, properly accelerate on the highway at 2000-4500 RPM several times (around 15 times) at full throttle to clear the soot buildup in the exhaust, and then immediately perform the inspection!

Is there visible smoke when accelerating at full throttle? Or did the inspector accidentally give the wrong DPF-FZ value for the inspection device?

The value is not just 2-3 times higher, but 30 times higher than tolerated
I don't think it has anything to do with the "freepusten" (blowing out air). I do that occasionally. Taxis don't only operate in city traffic
I also don't think it's the MKB (Motor Control Box). There must be something broken, but unfortunately, I can't figure it out with my own logic.
No error message, no hissing sound.

If the LLK (Low-Level Knock Sensor) were leaking, wouldn't it register an error? Something like a "suction tube regulation difference"?

Best regards

Should be working fine... but it hasn't been checked yet

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

Best regards

serdarg hat folgendes geschrieben:

The value is not 2-3 times higher, but 30 times higher than tolerated I don't think it has anything to do with the "freepusten" (breathing/venting). I do that occasionally. Taxis don't just operate in city traffic I also don't think it's the MKB. There must be something broken, but unfortunately I can't figure it out with my own logic. No error message, no hissing. If the LLK were leaking, wouldn't it then register an error? Such as a "suction tube regulation difference" or something similar? Best regards

30 times higher ... You would have to see some serious stuff... Errors occur when the LD is exceeded or underestimated!

With Mini-Leks, for example, it is possible to avoid errors when increasing the RPM without a load, as there is not enough LD and not enough exhaust gas mass to properly operate the charger.

What is the air mass and LD under full load in 3-4 gears at 1500-4500 RPM? Can you see soot when accelerating? If so, at what RPM and air mass and LD? Is the cat clogged? Compare with a manual transmission, what is the exhaust flow rate? Also, test the EGR valve experimentally.

[quote="T3Surfer"]

serdarg hat folgendes geschrieben:

The value is not 2-3 times higher, but 30 times higher than tolerated I don't think it has anything to do with the "free breathing"... I do that sometimes. Taxis don't only drive in the city center I also don't think it's the MKB. There must be something broken, but unfortunately I can't figure it out with my own logic. No error message, no hissing. If the LLK were leaking, wouldn't it then register an error? Such as a "suction tube regulation difference" or something similar? Greetings

30 times higher ... You would have to see a very strong wind... Errors occur when the LD (load) is exceeded or underestimated!

For example, with Mini-Leks, it is possible to avoid errors when increasing speed without a load, because there is not enough LD and not enough exhaust gas mass to properly operate the charger.

What is the air mass and LD under full load in 3-4 gears at 1500-4500 RPM? Can I see soot when accelerating? If so, at what RPM and air mass and LD? Is the cat clogged? Compare with a manual, what is the exhaust flow rate compared to other 1.9L TDI engines in LL mode? Also, let's try testing the AGR (Exhaust Gas Recirculation) experimentally.

Yes, it's about 30 times higher. I can't see soot myself. When running at full throttle, it emits a whitish, slightly bluish smoke. I can't say that it's producing black soot.

I need to measure the air mass and LD. What is clear is that when I accelerate hard from a standstill with full load, the car goes into emergency mode. The error message is then "Overload pressure control limit exceeded".

Sometimes this happens sporadically, and sometimes it just shows "- -".

Anyway, the car feels like there's a rubber band attached to the rear, and the car is trying to pull back.
Especially when I have 3-4 people in it, it really struggles in the low-speed range, it's noisy like a truck, and it's also very loud.
Comparable to a heart patient going up 3 floors :)

So, on Tuesday the car will be taken to the workshop. I asked them to find the problem, primarily checking the intake air path/turbocharger, and checking the timing belt settings.
There can't be any major timing belt issues with a PD engine, as I've heard repeatedly. But there must be some fine adjustments, such as valve timing and dynamic fuel injection start time.

What could be wrong with the 2.0 TDI timing belt if it's impossible for it to be 1-2 teeth off?

Something must be wrong there...
Yes, you can make mistakes with the ZR, the NW wheel is adjustable It must be exactly correct, either with the KW-alignment tool or the crankshaft marking, as well as the NW connector or Boher. Even a 3° adjustment can make a difference! I can't imagine adjusting the teeth; with 2 teeth, the valves can kiss the pistons.

Where would you get the information that your car has too little exhaust gas? Just because the LD is low? The sluggish acceleration from the low-speed range is also due to the low LD! Have you already compared the exhaust pulsing at the exhaust end with another comparable 2.0 PD-TDI engine by hand? Perhaps the catalytic converter is the problem!

Well, I'm curious to see if VW can fix it/completely fail, or replace unnecessary parts or swap out the entire engine for your car...

Sad that many "MASTER" mechanics know less than a "simple" mechanic like me, and yet they look down on me.

I'll also get the cat checked. I noticed yesterday that when idling, almost no exhaust fumes come out. Only when the car is cold does it emit a lot of white smoke, and when driving at night with nitrous, you can clearly see a gray-blue haze through the light of another car.

Otherwise, there's very little coming out, almost nothing from the exhaust.
And if you hold your hand in front of it, you can see how the gas pedal is being pressed in pulses.

I just don't understand the logic again. If the cat is supposed to be a catalytic converter, where does all the exhaust gas go then? It must go somewhere, right???

The exhaust is only slowly escaping through the clogged catalytic converter, which you can tell from the few or no pulsations in the exhaust with your hand.

I'm also asking you again, have you ever compared it to other cars with similar engines? That way you can make a good comparison! You can also remove the catalytic converter and drive without it! The TDI isn't that loud!