Intermittent Power Loss: Troubleshooting Guide

Hello,

Okay, here's my first post, and I'm including a log of the occasional performance issues I've been experiencing.

I've read quite a few articles on the subject, and I immediately had a friend create a log using Vagcom. Specifically, I had modules 3 and 11 logged.

I hope this is correct. Since I don't have any experience with data analysis, I converted it to an xls format. I hope someone can help me.

Last week, I had a problem with the N75 valve, and it was replaced. After that, it worked well for a few days. The performance was optimal and as it should be.

Now, we are seeing an increasing number of smaller performance drops. Sometimes, there's even a wave-like acceleration.

The vehicle is a 1996 Golf 3 AFN model with approximately 170,000 km on the odometer, completely stock and unchipped.

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Greetings.

Did you not have a CSV converter? Otherwise, import the data into XLS and experiment with what the column separation does. Then you'll get a table, and it's best to create some charts as well. No one will be able to assess these clumps of numbers at a glance...

Hello,

There's a CSV converter in VAGCOM. I just realized that. I ran it and hope it helps.

Sorry again .

Best regards,

Okay, that looks better. We should also be able to do something with the engine control unit (ECU) data. However, the information is missing (e.g., target and actual values, driver preferences, soot reduction, torque limitation). Also, you're using your left foot too much.

Quote:

Measurement recording via data logging. Assuming everything is generally okay, and when driving at full throttle in 3rd or 4th gear, you should log and analyze the following diagnostic data blocks (DTCs) within a speed range of at least 2500 to 4000 rpm.

persönlich wurde ich schon bei 1.000 rpm anfangen und mindestens der 4. Use the hallway.

Please provide the German text you would like me to translate into English. I will then provide the translation without any explanations.
Okay, I'm ready. Please provide the German text you want me to translate.

hello,

"I'm experiencing similar problems with my Toledo AFN. Fortunately, my father has the same engine and software. I've already replaced the mass airflow sensor, cleaned the fuel quantity adjuster, and adjusted it to the values from my father's Toledo during installation. I shortened the VTG slightly because it felt sluggish at low speeds, but the actual problem hasn't changed. The control rod is also loose and moves smoothly in and out."

The problem is as follows: When I accelerate fully, the engine pulls for a few seconds, then there's a pause, as if I'm letting off the gas, then it pulls again with full power for another 4-5 seconds, and then another pause.
Specifically in 5th gear, it drops briefly at 80 km/h, then reaches 100 km/h, and after 120 km/h, it drops again significantly, reaching just below 140 km/h.

Okay, so my LMM (likely referring to a mass airflow sensor) is relatively new, and I even swapped it with the one from another Toledo. Now, mine works even better, but the other one works slightly worse. However, the problem remains.

I've already done several logging runs with the 3-8-11 configuration, and a few times I've seen all the values drop significantly. In other logging runs, the RPM curve increased perfectly smoothly, even though there were noticeable dips. These dips are about 1-2 seconds long, and you only really notice them in the lower gears, especially when pulling a trailer.

The hoses are also relatively new and look okay. I once swapped the N75 valve with the EGR valve, and I've temporarily blocked the EGR valve with a piece of metal. I've also tried a different diesel filter.

Do you have any other ideas about what it could be? I'm happy to do some more research if you tell me what you need.

Kenny7 wrote:

Do you have any more ideas about what it could be? I can also do some research, just let me know what you need.

I would start by creating logs with a sampling rate of 3, 8, and 11, where the error is visible. Ideally, these logs should be recorded in "turbo" mode, if the engine control unit (ECU) supports it.
Possibly also each individual measurement channel (MWB) separately, to achieve a higher sample rate.

I prefer the whole thing as a processed Excel chart, while others prefer CSV files. If you provide both, you have the best chance of someone engaging with it.

Regards,
Guste.

PS:
1. Could you temporarily close the EGR valve for testing purposes?
Have you checked the charge air cooler to make sure it's not blocked, or at least carefully inspected and examined it?

guste100 wrote:

1. Could you temporarily close the EGR valve for testing purposes? 2. Have you checked the intake manifold for leaks, or at least carefully inspected and examined it?

Okay, the AGR (Abgasrückführung) is currently sealed with a metal plate. I just did a test run and processed the data in Excel as best I could. I can provide more information later, no later than Tuesday.

Today, I was also able to trigger an error code for the first time. Specifically, when starting from a standstill, the following error appeared.

Control unit part number: 028 906 021 EF.
"One error found:"
00519 - Manifold pressure sensor (G71)
28-00 - Short circuit to positive.

"Is that the pressure sensor in the MSTG? So far, I've never had any entries in the error memory for that. Except once, it was a vacuum manifold control issue because I had shortened the VTG too much."
"Are the overhangs a bit too large? If I adjust the VGT further out, they become a little smaller, but then the car loses all its power."

here are the logs, I'll create the other diagrams in Excel later, I have to leave right away.

The boost pressure is far too high. Either you've overadjusted the VTG rod, or something in the turbocharger control system is not working correctly.

Since you've already replaced the N75 valve, I would take a closer look at the vacuum hoses. There might be a kink, a tear, or something similar. If in doubt, just discard those few meters of hose and replace them with new ones.

Also, turn the boost pressure down a bit again if you want to continue using the turbocharger. You can no longer see the actual boost pressure with VCDS because it's outside the sensor's measurement range (which is why it's shorting to positive).

I would like to try setting a dedicated "11" log in addition to the current 3.8 and 11 settings.

I'll try my MSTG with my dad at his Toledo, as nothing on the hardware has been adjusted yet.

Regarding the VTG rod, I've read that you should shorten it until you achieve approximately 85% throttle response at 3900 RPM. I was at around 60%, and I'm still far from 85%. I'll do another logging session with the other car and see how much it overshoots and what the throttle response looks like. I shortened the rod because mine has always felt a bit sluggish. When you give it full throttle, nothing happens for the first 2 seconds, and then it suddenly kicks in. Maybe I need to find a middle ground. When I bought it, the throttle response was around 50%, which was during my first logging session, and I had no idea about VAGCOM back then.

I completely replaced the vacuum hoses once in the summer, but the problem was only occasional and rare back then, so I didn't investigate it further.
I'll watch it again.

Thank you in advance for the answers.

edit: I have now uploaded log2 and 3 as xls files.

What's the deal with the soot mass reading? Should it be above the target value, just like the torque limitation? Is the value calculated, or does it come from a sensor?
"Does this limit the power here? Am I understanding that correctly? You can see it clearly in the MWB8 data at the second log point. There's a dip in the torque curve there, which you can also feel as a loss of acceleration!"
I had cleaned it before, and that's also common. Currently, it's temporarily sealed with a piece of metal, and an older mass airflow sensor (MAF) is currently installed, which I need to replace with my new one .

Kenny7 wrote:

What is the purpose of the soot mass? Should it be above the target value, just like the torque limitation? Is the value calculated, or does it come from a sensor? "Is that what you mean by 'limited'? I think I understand correctly. You can see it clearly in the MWB8 data at the second log point. There's a dip in the RPM curve, which is also noticeable when accelerating!" I had cleaned it before, and that's also common. Currently, it's temporarily sealed with a piece of metal, and an older mass airflow sensor (MAF) is currently installed; I need to replace it with my new one

.
The fuel injection quantity is limited based on soot levels, which are determined by the air mass measured by the mass airflow sensor (MAF). Too little air results in a reduced fuel injection quantity to prevent soot formation. The low MAF reading is caused by a drop in boost pressure. Therefore, my comment about the turbocharger settings/control.

I've now turned the rod out a few rotations, making it longer. It worked a bit better, but I had about a 3-second pause after shifting before it engaged again. However, I noticed that the MSW (likely referring to a motor stroke width or similar parameter) value is changing. I was at 4.4 mg/hub, then I set it to 3, and it worked much better and with more force (because it's getting more "juice"^^).
Anyway, I was very unhappy with the VVT adjustment until I saw that the value was changing towards 5.0mg/hub and more. I've now corrected it again, and I think I'm on the right track. The turbo lag after shifting has become noticeably smaller again. All of this has happened with previously smaller overshoots.
Once things have cooled down a bit, I'll revisit this and take it a bit further.
Is it correct that the value changes along with it?

"Today, I also took my dad's Toledo for a test drive... So, the TV (turbo boost) on my dad's car is around 55%, but it fluctuates quite a bit compared to mine! However, you don't really notice that fluctuation while driving; it just pulls cleanly without any issues. The overboost is as it should be, about 0.1 bar. Mine is still slightly above that currently."
I've now reached just under 60% screen-on time (TV), with a longer viewing time. I'm going to further reduce this and see what happens.


edit: I'm still surprised that the problems only became so extreme in the last few weeks. Could it be due to the wet and cold weather and the lower temperatures?

edit2: I've now reached the other end (of the flagpole^^). The load cell setpoint is now only being reached with difficulty, and I even experienced an emergency stop once. So, I'm going to adjust it back a bit, then readjust the quantity adjustment, and I think it will work again }.

Okay, I've read quite a bit here and understood how the rod itself works, but I never adjusted it that far back because the car became incredibly sluggish. And I never dared to try the MSW (presumably a cleaning process) until I saw the instructions for it, right here in this forum.
Okay, first of all, thank you to everyone involved! I'm going to cut the rod into smaller pieces again until it fits.

Could someone please tell me which measurement blocks should be logged in this forum for the best possible diagnosis in the event of a power loss (approximately 50 horsepower), without any error codes being stored?

Hi,

1, 8, and 11 in the engine control unit. Also, add "ambient air pressure" from 10. There have been a few cars with faulty ambient air pressure sensors.

Otherwise:
I am unable to access external URLs, so I cannot translate the text from the provided link. Please provide the text directly, and I will be happy to translate it for you.

And: It's best to upload the CSV file without any modifications.

Best regards, Rainer.

I have now recorded MWB 1, 8, and 11, and I have added the log as an attachment.

There are full-load sections in the 1st, 2nd, and 3rd gears.

How can I add the ambient pressure? I only have 3 data blocks for recording in VAG 3.11.

Best regards.

EDIT:
The lack of performance wasn't a gradual decline.
After replacing the engine mounts, the lack of power initially occurred sporadically, even changing during the drive. For the past week, the problem has been constant.
Could it be that I disconnected any cables while jacking up the engine?

What I don't understand is why there's no error code stored?

Please help!

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

'lg.'
'Best regards.'

Quote:

And: It's best to upload the CSV file without any modifications.

The limitation due to air mass is insufficient.

Hello Rainer!

Hier nun eine komplett unveränderte csv datei von 2 und 3. Gang Volllast, und nocheinmal 1, 2. und 3. Gang Volllast leicht bergauf. (Über 3000rpm geht garnicht, dort endet auch im 1. G(related to strength)

The boundary is insufficiently defined by the air mass.
Sorry, but I don't know what you mean by that.

Thank you in advance & best regards.
P.

EDIT:
I have converted the CSV file into an XLS format. However, I am unable to provide any interpretation or analysis of the data.
Please help.

Best regards.
p.