TDI 1Z: Troubleshooting Engine Jerking/Hesitation

Like many others, I'm experiencing the problem with the stuttering/lagging.
TDI, 90 horsepower + chip (unknown manufacturer), 150,000 km.

- According to VAG.COM, the fuel injection timing is correct.
- Injection amount as well.
- Timing belt/tensioner was replaced 10,000 km ago, pump adjusted.
- Needle lift mechanism tested using the 'tapping test' at 3000 RPM.
- Test drive performed without the connected NHG (National Harmonization Guideline), but still experienced vibrations.
- The boost pressure control valve is blocked, but it still jerks/stutters.
- LMM is also fine.
- Diesel filters are clean.
- The jerking has been happening since I've owned the car, it's worse in the winter and less frequent in the summer.

Precise symptoms:
- Jerking/stuttering in 4th gear at lower outside temperatures (below 5°C), below 60 km/h, when driving at a moderate speed.
Acceleration.
-Jerking or stuttering in 5th gear at 90 km/h (approximately 56 mph) on a straight road during gentle acceleration.
It felt like I was choking.
The jerking becomes even more pronounced when you give it a lot more gas.
It only stops when you release the accelerator and press it again.

It has also improved somewhat since I added an additive to it.
Below 0°C, you can only drive in 5th gear at speeds of 100 km/h or higher.

I've already searched extensively in this forum and tried everything I could find.
Is there any other way to test if it's actually NHG?
The fuel consumption, at 5.5-6.3 liters per 100 kilometers, is also acceptable, I think.
I'm not sure what else could be the cause.
Does anyone know any help?

Hello.
Have you ever tried driving with the sender for the speedometer signal disconnected?
If it stops vibrating, then your flow control valve is likely stuck.
Try it out!

Best regards, Marcello.

@marcello

My 1Z has also started to stutter for the past two weeks, but only in 5th gear at 1400-1500 RPM.

During a test with the transmission control module connector disconnected, I felt that the issue was gone or reduced.

How can I get the quantity control valve working again - hopefully not just by replacing the pump ???

m;
12/95 (Model 96) 1Z CTN 156 Tkm G3 Variant.

I haven't been able to test the speedometer sensor yet.
I'll try it out sometime early next week.
I think it's probably in the range of 1300-1500 RPM when it starts to stutter.
Unfortunately, I don't have the exact data, so the values are estimates.
Can the NHG (presumably referring to a specific device or system) be electrically tested?
Can you tell if it's okay by taking it apart?

- Hae ??? TDI without tachometer?

- Expanding the NHG (likely referring to a specific engine component)? You want to disassemble the injector from cylinder 3 in your workshop? I wouldn't recommend that. Those parts are quite delicate.

m;

Where should I disconnect the tachometer signal for testing?
I also have some slight rattling noises around 1500 RPM. Now, I can't even reach 50 km/h in fourth gear .

The connector is located on the differential.

Right where the base for the cable lines begins.

It is black and has 3 poles.

m;

P.S.: Don't be alarmed, the fuel gauge's damping will also be off, the needle will jump around nicely when you're driving in curves and it's actually measuring something .

Hello.
A friend of mine completely disassembled the metering unit. During the disassembly, he discovered that metal shavings had accumulated inside. He removed them, and now the car is running great again.

Yesterday, I went to my acquaintance's workshop and had him disconnect the speed sensor connector.
The jerking was almost completely gone during the test drive.
The shifting felt a bit rough, but it's probably due to the emergency mode.
So, it's probably quite clear that it's the point machine.
Or what do you think?

I already asked Marcello if he could give me some tips on how to disassemble the ESP.
I was actually planning to have a friend of mine do it, but he's never done it before either.
So, could you perhaps share your experiences and tell me what to be aware of?
Do you need to remove the ESP (Electronic Stability Program) module, or can you open it while it's still installed in the vehicle and clean/disassemble the metering unit?
Do you need any special tools that you wouldn't normally find in a car repair shop?
Does the pump need to be reconfigured, even if it doesn't have to be removed?
Is it worth running the pump with this 'Liquimol' diesel additive?

The absolute last resort would be to replace the pump, the absolute last...

I would be very grateful for your help.

Hi,

lucckas wrote:

Yesterday, I was at my acquaintance's workshop and had the speed sensor connector disconnected there. The jerking was almost completely gone during the test drive. The shifting felt a bit rough, but it's probably due to the emergency mode.

This is not related to the limp-home mode. When the speed governor is disconnected, the comfort functions are unavailable, including: thrust cutoff, damping of drive shock (otherwise, even more transmissions would fail), and jerk damping.

Quote:

So, it's probably quite clear that it's the point machine. Or what do you think?

This suggests there is a problem with the point machine.

Quote:

So, could you perhaps share your experiences and tell me what to be aware of? Do you need to remove the ESP (Electronic Stability Program) module, or can you open it while it's still installed in the vehicle and clean/disassemble the metering unit? Do you need any special tools that you wouldn't normally find in a car repair shop? Does the pump need to be reconfigured, even if it doesn't have to be removed? Is it worth running the pump with this "Liquimol" diesel additive? The absolute last resort would be to replace the pump, the absolute last...

Disassembling (and correctly reassembling) a VP37 is not a trivial task. I wouldn't recommend anyone disassemble the pump without having first tried it out on a practice unit.
Even various Bosch services avoid opening these pumps. While replacing the entire pump is the most expensive solution, it's also the cleanest and most reliable.

Hello!

I also have a 1994 Passat TDI with the 1Z engine. The shaking starts for me around 1800 RPM and stops again at 2400 RPM, but it's only noticeable in 4th and 5th gear. I don't have any misfires or anything like that, so I'm ruling out the NOx sensor for now. The only plausible explanation would be the quantity control unit.

However, my colleague has the same Passat (94, 1Z) and experienced the same problem. First, he replaced the mass airflow sensor (MAF) - no change. Then he replaced the throttle body - still no change.
At some point, he had to replace the instrument cluster because of a crack in the housing. While doing so, he accidentally disconnected the connector for the GALA system (speed-dependent volume control). And lo and behold, the jerking/stuttering disappeared...
He already did the same thing on another TDI with a similar issue (misfiring), and the problem was solved!

In two days, we'll try it out on my Passat and see what happens.
Has anyone here had any experience with that?

I haven't been able to test the speedometer signal generator yet.
I'll try it out sometime early next week.
I think it's probably in the range of 1300-1500 RPM when it starts to stutter.
Unfortunately, I don't have the exact data, so the values are estimates.
Can the NHG (presumably referring to a specific device or system) be electrically tested?
Or can you tell if it's okay by taking it apart?


You can test an RCD (Residual Current Device) with a standard multimeter. Simply disconnect the RCD plug and set the multimeter to measure resistance. A functioning RCD should provide a value between 90 and 110 ohms, ideally around 100 ohms! (I don't know if this is temperature-dependent, but it's probably best to measure it when the device is cold!).

I'm in the process of creating a small guide on how to open the quantity setting mechanism.
Please be patient.

Greetings, Marcello.

@marcello: A guide would be fantastic! I'm about to go to the Bosch service center. $$$

Greetings to all those affected by Ruckl.

@marcello
Sure, a guide for this could potentially save some people from costly repairs (if it works).

I'm looking forward to it.

Regards,
Hermann.

@marcello

And? How's it going?