1.9 TDI 66kW ALE: Troubleshooting & Expert Advice

Hello everyone,

I would have liked to post in the engine technology forum, but I don't have the necessary status yet.
I have a question about my Golf III Variant, manufactured in 1998, with a 1.9 TDI 66kW (ALE) engine, a KKK variable geometry turbocharger (not yet a VTG).

Searching the forum and tracking various investment accounts hasn't really helped me gain much insight so far.

I think I'm experiencing a loss of power or a lack of torque. It's not really dramatic, but it's not fun anymore.

Habe natürlich zuerst auf den LMM getippt, da er mir beim Beschleunigen auch teilweise in die Rauchgrenze reinläuft. rosa ist Einspritzmenge Fahrerwunsch, gelb Drehmomentbegrenzung und blau Rauchbegrenzung bei Vollast im 4. Gang



But that's a minimal adjustment, and if I increase the air mass with a diode to its maximum, I don't subjectively experience a significantly better driving experience (it just runs slightly higher in the torque limit).

Two things have come to my attention:

"I seem to recall that the acceleration when flooring it in 3rd gear used to start around 1900/min (since the ALE engine produces its 210Nm of torque at 1900 rpm). However, I often drive different TDIs, and it's possible that I'm mistaken. What are your experiences with this engine?"
Today, I notice a slight boost in energy around 2200-2300 hours, but it's not really that impressive.

"Regarding top speed, I'm getting around 170-180 km/h today according to the speedometer, and it takes me a relatively long time to reach the maximum speed. Does anyone else happen to have a Golf III Variant and can confirm these values? I think it used to be faster."

When I check the boost pressure at full load in 4th gear, I notice that the target boost pressure is only reached at approximately 2200 to 2300 RPM. Can someone confirm whether this is normal, or whether the full boost pressure should be reached earlier?

Blue = RPM, pink = target pressure, yellow = actual pressure.




It's also noticeable that in the partial load range, i.e., when I try to maintain a constant speed, the target boost pressure is not reached. This may be because it's not regulated in this range, but rather set, and there might be a slight leak somewhere, or the turbocharger may be worn. (At full load, it's regulated, so the wastegate opens later, and the boost pressure eventually stabilizes (later), or something like that).






Can someone help me? Perhaps by comparing my data with theirs, which was recorded with a healthy engine?

What else could it be?

* Hanging AGR valve? How do I test it? Do I have to remove the entire intake manifold?
* Dirty intake manifold? But then the air mass would be too low, right? Is it really that significant? If the engine is running poorly due to a lack of air but receiving the full amount of fuel injection, would it produce a lot of black smoke during a diode test? I haven't paid attention to that yet.
* Experiencing issues with back pressure from the exhaust system? How can I rule this out without having to remove the catalytic converter?


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

"Hello"
ElCapitano.

Okay: I've noticed an increased fuel consumption lately. Previously, I usually had a consumption of between 5-6 liters, but now it's always over 6 liters per 100km.

Hi,

I also have an ALE variant from the year 1997 with 201,000 km on the odometer.
So far, everything has been fine without any major problems.
My cruising speed on the highway is usually between 170-180 km/h, and on a straight road with no headwind, I can reach almost 195 km/h.
I can't say anything about your diagrams.


Greetings.

Clemens.

Hello,

Okay, so the boost pressure is always regulated. There is no option to switch to a different setting.
It would also be interesting to know the duty cycle of the valve used to control the boost pressure.

If the boost pressure cannot be regulated properly, it could be due to a leak in the charge air system. In this case, the exhaust energy only provides enough boost to reach the target pressure during brief periods. With larger leaks, it's not even possible. You can clearly see this by the duty cycle of the boost pressure control, which will then reach its maximum limit.

At 201,000 km, the turbocharger itself may also be clogged, which can prevent it from reaching the desired boost pressure. You can see this in the duty cycle.

First, I would clean the vacuum sensor of the turbocharger. This is often where the problem lies. Please read other threads on this topic for more information. It's a quick and inexpensive fix.
If that doesn't help, you'll probably have to start the 'big' search.

Ah yes, my old car with the 90 hp AHU engine also had its maximum torque at 1900 rpm, so you're right with your assumption.

Best regards, Jochen.

Hello Jochen,

Thank you for the information.

Here's a diagram showing the duty cycle for the boost pressure control.



I understand from this that the wastegate opens completely when it's at 100% activation. But what is the minimum setting? And why is it controlled at 35% until the target boost pressure is reached?

Regards,
Christian.

PS: In my opinion, the wastegate is controlled via a pressure-sensing diaphragm. Therefore, in case of a defect, there should eventually be too much turbocharger surge, not too little. I don't have a variable turbine geometry (VTG) system!

The duty cycle is inverted.
A 0% display reading indicates 100% PWM at the valve, resulting in the maximum possible boost pressure.

However, the motor does not fully utilize the duty cycle for the boost duration setting (e.g., it only uses a range of 5% to 85%, but this is just an example; check the database for the exact values).

It is clearly visible that the maximum pressure builds up very slowly. Therefore, your assumption that you get a 'turbo boost' at around 2200 rpm is correct. The diagram shows this very clearly. Furthermore, it can be seen that the desired pressure can be regulated.
Therefore, I am quite certain that you have a stuck vacuum sensor.

This can also explain why your engine sometimes experiences incomplete combustion. This is because the slow build-up of boost pressure results in a lack of air in the combustion chamber.

I wouldn't suspect a leak in the intercooler system right now.

Clean the vacuum pump, and the turbo should respond faster.

Best regards, Jochen.

Hello there,

Regarding the turbocharger ratio, boost pressure, etc., in a wastegate system, I need to make a few comments.

First of all, it's correct that the pressure vessel operates under pressure.
Furthermore, the WG regulation is a regulation of a higher order compared to the VTG regulation.

In the VTG system, the can is fed from the vacuum system with a storage buffer. Consequently, the duty cycle directly reflects the position of the guide vanes.

The pressure that opens the wastegate via a pressure diaphragm is the boost pressure itself.
If the boost pressure control valve (N75) is left unactuated, meaning open (100% duty cycle), then the total boost pressure acts on the diaphragm.
This already constitutes a purely mechanical pressure regulator. The boost pressure that is achieved depends on the design of the surge tank, turbocharger, etc.

Actually, the VAG wastegate systems in TDI engines are designed to regulate a pressure of approximately 1.5 bar.
The wastegate doesn't make a "popping" sound at 1.5 bar and then open abruptly; instead, it opens continuously as the pressure increases.

Above this pressure regulator is the EDC (Electronic Diesel Control), which essentially prevents the turbocharger from naturally limiting the boost pressure and instead regulates it to 1.9 bar.

When the N75 valve is activated, it closes the connection on the compressor side, specifically the pressure sensor. At 0%, the valve would constantly receive 12V.

The duty cycle in the wastegate (WG) system indicates what percentage of the boost pressure acts on the WG valve. (Excluding losses in the hoses).

That's why it makes sense that a small percentage corresponds to high boost pressure, and vice versa.

The upper and lower limits are determined by Volkswagen and can vary from engine to engine.

Okay, regarding your boost pressure, I also have an AGR with a wastegate. The boost build-up looks very similar to what you're experiencing. The only difference is that I reach the target pressure a bit earlier, and the duty cycle is much higher (80%).

Unfortunately, I can't say whether the low duty cycle you're experiencing indicates a problem or is simply normal for your motor.

I would like you to perform a measurement with the electrical connection disconnected from the boost pressure valve. A boost pressure of approximately 1.5 bar should be observed. Also, please run the engine up to 4000 RPM to check the pressure at a slightly higher speed.

Therefore, it is possible to determine how the wastegate itself is functioning and whether there is already a fault present.

It seems that the inability to adjust the boost pressure at low loads is normal for the WG (wastegate). From the diagram you provided, where you were trying to maintain a constant speed, I can see that you experienced slight lag. The drop in engine speed, along with the decreasing boost pressure setpoint, indicates a reduced fuel injection volume.
If you have a GRA (presumably referring to a vehicle with a speed limiter), try driving it at 130 km/h on the highway; you'll definitely be within the normal operating range.

Regards,
Malte.

That sounds very familiar to me - I think I'm having the same problem.

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

"see here:"

This phrase is often used to direct the reader to a specific location in the text or on a webpage. It can also be used to indicate that the reader should look for more information elsewhere.

For example, the phrase "see here:" might be used to direct the reader to a footnote or a table that contains more information about a particular topic. It could also be used to indicate that the reader should consult another source, such as a website or a book, for more information.

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The phrase "see here:" is a versatile phrase that can be used in a variety of contexts. It is a useful tool for writers and readers alike.
http://gload.de/preview.php?file=d10eb4c8f8bd5b3c6d5bab744.jpg

or here:
http://gload.de/preview.php?file=a2409844457363b200fe812e2.jpg

I'm also quite at a loss.

Sure, here's the translation:

"lg" is a German abbreviation that stands for "liebe Grüße," which means "best regards" or "warm greetings." It's commonly used in emails, letters, and other forms of communication to express affection or goodwill.

Hi,

Regarding the low duty cycle within the normal operating range, which is approximately 50%, I still believe that this is normal for some engines with wastegate control.

"I've also seen this with a 5-cylinder Audi engine, for example. Within the normal operating range, the duty cycle only reaches around 50% (with a lower limit of 14%), and the boost pressure is perfectly fine and builds up quickly."

It is also noticeable that the control system reacts only very slightly to disturbances (fuel injection quantity), while the boost pressure remains perfectly within the target range.

Compared to my AGR (Abgasrückführung), the duty cycle increases to 80% at full load (3000 RPM). In the regulated range (3000 RPM on the highway with GRA - Gas Rückführung Anlage), the duty cycle varies between 30% and 80% depending on the injection amount. The target value is maintained. Therefore, the duty cycle reacts with significant fluctuations to disturbances.

I believe that these different behaviors are due to the design of the wastegate, specifically the pressure sensor and, above all, the magnetic valve (N75).

It seems that the N75 valve from the AGR (Abgasrückführung - exhaust gas recirculation) system and the N75 valve from the APA (Abgas-Partikelfilter - particulate filter) system are fundamentally different.
The N75 valve of my AGR system makes a noticeable clicking sound when voltage is applied, and you can also hear it clicking at the frequency of the duty cycle.
The N75 relay isn't clicking. When directly connected to voltage, you can hear a very faint "click" (if the surroundings are quiet), but it should still be working.

I now understand that in the WG system, two methods of electro-pneumatic conversion are used:

In the AGR system, the N75 valve opens and closes in sync with the duty cycle, alternating between open and closed. The desired boost pressure is generated in the wastegate (WG) can through the duty cycle applied to the pressure supply. This means that sometimes there is boost pressure, and sometimes there is the pressure that exists before the turbocharger (as can be seen by looking at the hoses).

In the APA system, the N75 component functions differently; it converts the duty cycle into a specific opening cross-section. Therefore, it operates continuously and adjusts the resulting voltage based on the duty cycle, effectively increasing or decreasing it. (It's possible that the frequency derived from the duty cycle might be higher in this case.)

"To my understanding, this would definitely explain the different behavior. If the EDC initially sets the cross-sectional area for 1900 mbar, it largely regulates itself. Since the control air is the same as the boost pressure (as mentioned in my previous post), the duty cycle in that area reacts very weakly to the injection quantity."

Regards,
Malte.

Hi,


Since the target and actual pressure are okay, and the soot limiter only kicks in at higher RPM, I think either the mass airflow sensor is defective (already ruled out by a diode test), or unfortunately, your engine is suffering from a blockage (e.g., a clogged catalytic converter, a crushed or defective exhaust).

Best regards, Rainer.

Okay, so it seems I've managed to fix the problem (although I'm not entirely sure if it really solved everything).

1. A hose clamp on the outlet of the turbocharger's compressor was not fully tightened (I didn't notice this twice during my initial inspections, but I think it was still relatively tight).

2. Replaced the diesel filter. The old one was a cheap ATU filter that had already been used for quite a few kilometers. I now have a Mahle filter installed.

Unfortunately, I haven't had time to create any logs yet. Maybe I'll get around to it eventually.

Anyway, the car is noticeably running better now. I can't say for sure if it's back to its full performance from before. My driving experience is a bit confused now... the more you pay attention, the more insecure you become eventually...


"Anyway, thank you to everyone, and I'm sorry for the 'inconvenience' caused by what seemed like such a simple issue. I really could have figured that out sooner."

Greetings.
ElCapitano.

Okay... I'll re-install the diode soon. Maybe it was trying to inject more current, but the filter prevented it.

Would that be a good idea, or would it have a different effect?