Cold Start Problems? Emergency Mode Explained.

Hello everyone.

Ich fahre seit 4 Monaten nen Passat 35i Bj. 09/96 mit AFN Maschine (81kW ohne Tuning) mit 171 Tkm auf der Uhr (6000 Km davon ich). Ist mein erster TDI. Mir ist aufgefallen daß der Motor bei Außentemperaturen unter ca. 14 Grad und nach einer Standzeit von mehreren Stunden auf den ersten paar hundert Metern das Gas äußerst schlecht annimmt. Ungefähr so wie im Notlauf. Ich hatte aber noch nie nen Notlauf erlebt, daher kann ich auch nicht genau definieren ob der wirkliche NL so ist (subjektiv wie ein 90 PS Benziner bei gleicher Drehzahl wie TDI, also ne lahme Ente ). Die Vorglüh-LED blinkt übrigens nicht. Nicht daß ich den Motor nach dem Kaltstart derart quäle aber das ist mir mal aufgefallen als ich etwas flotter nach nem Kaltstart aus ner Ausfahrt rausfahren mußte, null (vom gewohnten) Turboschub ab ca. 1800 Upm. Der Turbo kommt selbst bei über 2500 Umin nicht. Aber nach ca. 1/2 Km ist dieses Phänomen wie weggeblasen. Jetzt wo´s eh wieder kälter ist fällt mir das bei fast jedem Kaltstart auf. Ist dies vielleicht so gewollt um den kalten Motor (bei winterlichen Temps.) vor Volllast zu schützen oder ist bei mir was faul??? This problem doesn't bother me too much because I don't really let my car when it's cold anyway, but this question still occupies my mind, and I'm wondering why THIS is the case.
'Thanks.'

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Hi,

I think your self-protection theory is correct. Even when it's really cold, my engine doesn't perform much better than a naturally aspirated diesel. Presumably, the timing is deliberately set in a way that keeps the exhaust emissions within an acceptable range and extends the engine's lifespan.

A friend of mine once owned a NISSAN Patrol Turbodiesel. He always drove it hard, until one day the cylinder head cracked.

Regards,

Eike.

Hi,

ich hab nen AFN 10/96 und kann keinerlei Leistungseinbußen nach einem Kaltstart festellen. Strange.

Best regards,
René K.

Hi,

Have you ever thought about a VTG adjustment that is stuck in a cold state?
You can find more information about it on the forum and on Rainer's page.

Bertil wrote:

Have you ever thought about a VTG adjustment that is hanging in a cold state??? You can find more information about this in the forum and on Rainer's page.

Hi everyone,

I can only fully agree with Bertil from my own experience .

Hi.

First of all, thank you for your responses.
I had also considered the VTG. Could the problem with the sticking VTG also be due to increased soot emissions? Although the previous owner mostly drove long distances, he certainly didn't drive slowly (it was a company car ). I would say that mine produces quite a bit of soot, and the exhaust fumes smell quite awful (it smells almost like an old two-ton truck from the military ). Could this be due to the fuel injectors??? Would replacing the fuel injectors with new ones solve these problems with soot, the sticking VTG, and the smell? I have often considered replacing them, but I don't want to incur the financial expense right now because the engine, apart from the problems mentioned above, is actually still in top condition (it always starts on the first compression at any temperature ).

Best regards,

ampac wrote:

... I would say that mine doesn't produce very little soot, and the exhaust fumes also smell quite awful (almost like an old military truck ). Could this possibly be due to the fuel injectors??? ...

Okay, a TDI (or the newer CR engines) doesn't smell like soot. A TDI engine has a more "pungent" smell. Someone once wrote that it smells like ether. If a TDI engine smells strongly of soot, then I would have the catalytic converters checked.
If you still have the original injectors at 171,000 km, I would replace them immediately. JoergS, Rudi, myself, and several others here on the forum have experience with new injectors, and all of us have observed significant changes in engine behavior (soot, smell, performance, fuel consumption) after replacing the injectors.

Aha.

The fuel consumption isn't exactly moderate either. I haven't driven it for less than 6 liters. I do press the accelerator pedal quite hard from time to time , but rarely exceed 3000 RPM (except on the highway, of course, but I rarely drive there). Otherwise, in everyday use, I stay around 2250 RPM. My father drives his 1Z for under 5 liters and also keeps it at 2250 RPM. Mine actually smells very strongly, I would say. I once drove a motorcycle behind an Opel DTI, and it smelled almost exactly the same. It seems like fine plastic particles (!) are being injected, which then burn, at least that's what my nose tells me. You probably know how horribly burning plastic smells (that's kind of how my engine smells, I think). But soot smells completely different.
'Are ESDs also available as replacements from Bosch? Are they just as recommended as new ones, and what's the price difference between new and replacement parts? Thanks for your answers.'

Best regards,

By the way: What exactly wears out in the injectors that causes them to need replacement after a certain mileage? Does this have anything to do with the spray pattern or atomization?

ampac wrote:

By the way: What exactly wears out in the ESDs (electrostatic discharge devices) that causes them to need to be replaced after a certain amount of use?? Does this have anything to do with the spray or jet pattern???

Hi,

Your guess is already quite right.
Please read this: /viewtopic.php?t=1356
or also here: /viewtopic.php?t=1365

Hello.

Okay, I've done some pull tests. According to Ulf's DZR (drag coefficient), my car should take 7.503 seconds to accelerate from 2000 to 4000 RPM. However, I'm getting an average of 8.612 seconds (I did multiple tests for accuracy). Is that time still within the tolerance range? It's possible that I miscalculated the weight of my car, but to achieve that time, the Passat Variant 35i would have to weigh over 1650 kg, which it definitely doesn't. I think I'm off by no more than 50 kg, and even then, there's still a 1-second difference between Ulf's DZR and my measurement.
During the tests, I also noticed that the turbo boost intermittently cuts out between 3000 and 4000 RPM, and then comes back on, etc.
I also fiddled with the pushrod of the VTG today. It can be adjusted by pulling on the vacuum line, but it becomes quite stiff in the last few millimeters and then makes creaking noises (similar to a rusty spring, or something). Can anyone make use of my measurements and tell me if this is still okay? Unfortunately, I don't have the ability to read the data from the EDC (I don't have a laptop ), which might make things a bit clearer.

Best regards,

Hi,

This surge in power between 3000 and 4000 rpm indicated that the variable geometry turbocharger (VTG) was experiencing difficulty.
Applying a good amount of copper anti-seize compound helped me.

Best regards,
René K.

Na klasse. Hab nicht mal nen freien Blick auf´s Gestänge, wie soll man da etwas schmieren (alles zu verbaut). Bin mir nicht mal sicher ob das Gestänge sich 1 cm hin u her bewegen läßt. Nach dem 'fühlen' nach würde ich sagen dass das etwas weniger ist. Macht what's up?

Regards,

ampac

Hi,

I haven't seen the engine bay of a Passat before, but I was able to access it from above (on a Golf 3) after removing the intake manifold from the air filter to the turbocharger (it was only held on by three screws).
I didn't measure it exactly, but I think it was about 1 cm.
'I also experienced those squeaking noises, but it was coming from the lower end (with minimal pressure buildup). Even repeatedly moving it back and forth with a syringe didn't help (though it definitely worked out my arm muscles). I was almost ready to completely remove the turbocharger, but then I decided to get some copper paste and try using it => so far, no more problems. It was the linkage that was causing the issue, not the internal adjustment mechanism as I initially suspected.'
Do you happen to have an LDA (Linear Discriminant Analysis) model available? It's very helpful for observing the behavior of the system.

Best regards,
René K.

Hi.
@zzzzzz: Thanks for the tip about the copper...
A new LDA would probably not be a bad idea. I would have to buy or borrow one. Without disassembling the shaft, applying copper grease probably won't do much. My engine is also installed transversely, but there isn't much space left between the splash shield and the engine (where the turbo is located). Would I really have to disassemble the entire intake manifold? Yesterday, I drove 100 km on the highway at full throttle. Now, the VTG doesn't get stuck immediately after starting, but that's not a permanent solution.

Regards,

Arnold.

zzzZZ wrote:

I was almost ready to completely disassemble the turbocharger, but then I decided to get some copper paste and try using it => so far, there have been no more problems. It was therefore a problem with the linkage, and not, as I initially suspected, with the adjustment mechanism inside the turbocharger.

Hi René,

If you remember, I'd be interested to know exactly what you used the paste for.

"In my case, both the can and the adjustment lever leading to the loader were loose, while the internal mechanism seemed to be jammed. This resulted in about 1 mm of vertical movement, including the lever, and the lever always felt "weak" or unresponsive on the outside."
The aforementioned 1 mm clearance likely corresponds to the play between the lever and the internal (jamming) mechanism.

That is, in my case, I would only have been able to apply the paste from the outside to the parts that didn't need it anyway.