Beschleuningsaussetzer beim 1,9 PD TDI 85KW (MKB AJM) | Posts 16+

Hello Stefan,
What kind of engine and car do you have? What's the year of manufacture, mileage, etc.?
Best regards,
Günther.

turborie wrote:

It started with a noticeable loss of power from idle up to approximately 1800 RPM. This has progressed to the point where performance in this area is almost completely absent. I'm almost afraid to get back on the highway. I haven't noticed any side effects: no jerking, no black smoke, and no increased [something - the original German is incomplete here]. Fuel consumption: none. No hissing sounds. Engine compartment is completely dry! Oil and coolant levels are good, air and fuel filters are new, oil change completed. New oil filter installed, strainer in the tank cleaned, hoses checked. After checking everything, a vacuum leak is unlikely... Does anyone know the magic ingredient? Which sensor or component should be tested or replaced? Help!!

Well, one possible magic ingredient is called LDA.

Otherwise, there is also a guide here for systematic troubleshooting, which covers more than what you have checked so far -> Hits in bold letters 2 .

How about the pre-injection pump on the cylinder head? It's known to cause problems with jerky acceleration. You can also have a specialist measure the pre-injection pressure using special tools. If that's not within specifications, then it's clear why your car is jerking.

Best regards,
Mattes

Mattes AFN wrote:

How about the pre-injection pump on the cylinder head? It's known to cause many problems, especially jerky acceleration.

Hmm, the pre-lift pump (if present) is located in the tank, and that component on the transmission case is officially called a tandem pump.

Are tandem pump failures really that common, or are there any empirical values indicating which conditions favor low pressure?

In this forum, it would be (if I recall correctly) the first case of its kind... that's also why it's not mentioned in the article about common mistakes.

Hello everyone, hello Ulf.

First of all, I'd like to apologize for my behavior yesterday.
I somehow immediately realized that the top post in the list was addressed to me!
I'm embarrassed and all I can say is: sorry!
Give me the opportunity to correct my mistake.

So:

Engine: MKB, 140,000 km mileage, timing belt replaced at approximately 120,000 km (by a specialist workshop).
Approximately 30,000 kilometers per year, and most of that is highway driving.
New LLM since yesterday.

The following phenomenon is now observed: approximately 25 horsepower of residual power (purely subjective).
Fuel consumption according to the combination instrument: within city limits, up to 3rd gear, 22.3 liters.
Autobahn bei Vollgas (momentan ca. 100 km/h) 6,3 Liter. Upside-down world!

The repair shop refused to read the error codes and data blocks.
Weak justification, but I understand some aspects of it (specifically the extremely high costs associated with error diagnosis).

Tomorrow, a friend who is a certified Volkswagen mechanic will connect the diagnostic tool and read all the necessary data.

By the way, the tandem pump is located directly on the engine and is driven by the camshaft.
driven. It also generates the vacuum for the brake booster.
Is it possible that when braking just before a car that is about to stop, I could be in neutral?
I intend to feel even the slightest irregularity in the machine's operation, or can I?
Am I just imagining this? Could the tandem pump actually be the problem?
I'm going to do some more research on my own for now, and I'll let you know if I have any success.
Okay, and I'm also aware of the possibility of failure, right?

Sorry about the blunder...

Best regards, Stefan.

ulf wrote:

Are tandem pump failures really that common, or are there any empirical values indicating which conditions favor low pressure? Clear answer: YES! The tandem pumps are listed in VW's documentation as the number one cause of jolting... Why is that?

The tandem pump must properly force the fuel through the cylinder head; otherwise, there is a risk of air bubbles forming because the fuel is not cooled sufficiently. This can lead to engine jerking.

Hello everyone, hello Ulf,
Engine: MKB, 140,000 km mileage, timing belt replaced at approximately 120,000 km (by a specialized workshop).
Approximately 30,000 kilometers per year, and most of that is highway driving.
New LLM since yesterday.

The following phenomenon is now observed: approximately 25 horsepower of residual power (purely subjective).
Fuel consumption according to the combination instrument: within city limits, up to 3rd gear, 22.3 liters.
Highway driving at full speed (currently about 100 km/h): 6.3 liters. Upside down world!



@Stefan:

I don't know if this will help you, and hopefully it won't confuse you even more.

I'm using a very similar setup to yours, but with OBD tuning. Just search for the author 'ttns4' to find more information.

1.)
I would probably spend around 30 euros to replace the diesel temperature sensor with a water temperature sensor (instead of buying a new diesel temperature sensor, but you'll almost break your hands trying to do it yourself; it's best to have someone else change it).

'@ quote, I believe this is from Ulf:'
Approximate resistance values at 0/10/20°C:
038 906 081 B Diesel: 15 kΩ / 10 kΩ / 6 kΩ
06A 919 501 Water: 6 kΩ / 3.9 kΩ / 2.6 kΩ

If you're lucky, it might be due to this; in my case, it definitely helped, although I had a problem with the exhaust flow up to around 1900 RPM. It didn't misfire, but I temporarily blocked the EGR valve as a test...)

At worst, you've wasted 30 euros. (The exchange rate is so bad, it feels like you're getting ripped off.)
'I've also had the (N75? I think that's what it's called) boost pressure control valve replaced several times (it wasn't working correctly right away). It's located on the left side, when viewed from the front, near the mass airflow sensor (MAF), with vacuum hoses and an electrical connector. You might want to replace it yourself just to be sure.'


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

'2.)'

'If I were you, I would definitely try to return that supposedly new Bosch mass airflow sensor (MAF). The VAG workshop will likely put up a strong fight, as they'll want to run all sorts of tests...'

'With me, the new mass airflow sensor was *much* worse than the old one, as I mentioned in one of my posts.'
Nobody would believe that!
My conclusion is that new products are often worse than old ones, especially the refurbished ones; I've experienced this three times already!

3.) Make absolutely sure to have the tax data checked again after the timing belt replacement. If the problem started then, don't believe everything you're told (even if it seems partially true!). Be careful that the problem isn't delayed or ignored.

After the first timing belt replacement, it was stated that everything was fine and had been checked by three workshops (VAG dealerships!!!), but it wasn't actually okay.

Thanks to the information about the timing belt replacement (I think it was from Ulf), after another timing belt replacement at approximately 140,000 km at another large VW dealership, it finally worked out, and the car is now running satisfactorily.

'Out of desperation, I ended up uploading different tax data through the OBS interface on my own device (of course, not through Volkswagen's system...)'
The car is running now.

It might sound a bit bitter, but if possible, I don't want my car to go to a Volkswagen workshop because they simply can't do it .


I wish you good luck; hopefully, you'll have to pay less of a learning price than I did.

As I mentioned, this is my personal experience. I can't use a VAG-COM diagnostic tool myself, but the workshops have them, and they probably can't fix it either. There might be exceptions, but so far I haven't found any.

Regards,
ttns4

Thorsten

Bertil wrote:

The tandem pumps are listed in VW's documentation as the number one cause of jolting... Why is that?

Okay, this is a case that can be used to supplement the article about common causes of errors -> I'll add it soon.

Quote:

The tandem pump must properly push the fuel through the cylinder head; otherwise, there is a risk of gas bubbles because the fuel is not cooled sufficiently. This can cause jerking.

So, the throughput is low.
Do you happen to know where the cause of the problem usually lies within the pump?
Leaks or losses in the pump itself, or a weakening pressure relief spring?

The problem with the fuel pump could, in my opinion, also be diagnosed based on the diesel temperature (instead of installing a pressure gauge).
The lower the flow rate, the higher the exhaust temperature, due to the longer residence time of the diesel fuel in the combustion chamber.
Then, it would only be necessary to define a standardized measurement procedure (e.g., a DZR test?) and specify approximate target values for the temperature (or also for the temperature increase between the beginning and end of the measurement?).
"Hast du eine Idee?"

"Do you have any ideas?"

- and edit -

Hi,

Quote:

I would probably invest around 30 euros and replace the diesel temperature sensor with a water temperature sensor (instead of buying a new diesel temperature sensor, but you'll almost break your hands trying to do it yourself; it's best to have someone else change it).

I would strongly advise against doing that!

First of all, it's illegal tuning, and secondly, it's a fact that something is broken on the car. If it can only go up to 100 [km/h], then it's not just missing 3 or 4 horsepower; there's a significant problem. Trying to compensate for that with tuning is a very, very bad idea. If you're going to tune the car, fix the underlying issue first; otherwise, it's pointless.

Due to the diagnosis: Please also log data while driving.

Best regards,

January.

Tuning? Is a new mass airflow sensor already considered tuning?
I also replaced the fuel filter. Do I need to have that registered?

No, no, I don't want to modify it; I just want my performance back.
And I'm talking about the full 115 horsepower, please. Right now, I would estimate it to be around 28 horsepower.

Hi,

Quote:

Tuning? Does a new mass airflow sensor already count as tuning?

No - unless you build yourself a replacement device that always works and provides the exact right values.

I was referring to the (absurd) suggestion to replace the diesel temperature sensor.

Best regards,

January.

turborie wrote:

Tuning? Is a new mass airflow sensor already considered tuning? I also changed the fuel filter. Do I need to have that registered? No, no, I don't want to modify it; I just want my performance back. And I mean the full 115 horsepower, please. At the moment, I would estimate it to be around 28 horsepower.

Well... maybe print out the troubleshooting guide for loss of power and hand it to the VAG mechanic.

I'd be curious to hear what someone thinks about that... and of course, I'm interested in the result.

No way, I'm not breaking my fingers over this...
That will likely be the final consequence. If everything else has been exhausted.
Just for testing purposes. This should definitely work.

- edit and delete -

turborie wrote:

Yes, it's possible that the tandem pump is the number one cause of the jolting. But, damn it, it doesn't budge even a little bit!

"Fettnäpfchen xx ??" translates to "Awkward moment xx ??" or "Blunder xx ??" in English. The exact translation depends on the context of "xx".

The title in the original thread is: Acceleration issues with a 1.9 PD TDI 85KW (engine code AJM).

To some extent, these are just minor issues... if you have a different problem, please create your own thread and don't attach yourself to other people's threads!


@Ulf

Ulf wrote:

Aha - a case to supplement the article about common causes of errors -> I will do that soon.

I thought you already had that .
During my search for used parts on the AXR forum, a tandem pump was listed at the top.

Quote:

So, the throughput is low. Do you happen to know where the cause of the problem usually lies within the pump? Leaks or pressure losses within the pump itself, or a weakening pressure relief spring?

You are asking questions...
Unfortunately, no! I haven't opened one of those yet and formed an opinion about how it works.

Quote:

"In my opinion, the problem with the fuel pump should also be diagnosable based on the diesel temperature (instead of installing a pressure gauge)." The lower the flow rate, the higher the exhaust temperature, due to the longer residence time of the diesel fuel in the combustion chamber. Then, it would only be necessary to define a standardized measurement procedure (e.g., a DZR test?) and specify approximate target values for the temperature (or even the temperature increase between the start and end of the measurement?). Sure, here's the translation: "Do you have any ideas?"

No, not really, at least not right now.
The problem here will be the environmental conditions. If it's cold outside, you get a completely different measurement than if it's warm.[/quote]