Boost Issues: Troubleshooting with Logs

Hello.

Now that I've been reading for a long time, I really need to get some more detailed advice. I was able to gather some information from the search results, but I'm still a little unsure about my problem.

This is a Golf 4 with a 90hp (ALH) engine, approximately 204,000 km on the odometer, and it hasn't been chipped. However, I've recently started using a "10-cent tuning" feature occasionally (it can be activated), but only for a few seconds at a time.

Occasionally, the emergency mode would activate during faster highway driving, and I've already identified a few potential causes for it.
However, since I bought the car (approximately 10,000 km ago), it has had a slight whining noise at lower RPMs, which has always concerned me, especially when the engine is cold.

For a few days now, I've been using an LDA (likely referring to a specific type of equipment), and during the first full-throttle acceleration, the hose burst (at approximately 2 bar). This strange feeling that overcame me at that moment is what prompted me to reach out.

Now, however, I've acquired an old laptop and a VAGcom device and performed a data logging session: Perhaps you can see more in this than I do, but unfortunately, I don't recognize any clear errors here. According to the LDA (likely referring to a sensor reading), I quickly reach 1.7 bar with a 10-cent tuning adjustment, but even without that, the LDA occasionally reaches these levels.
I am now trying to keep the load limit (LD) as low as possible. I haven't been able to access the vertical travel gauge (VTG) yet to check its smoothness, but I will do so as soon as possible.

Interestingly, only one out of my three logs seems to be providing any useful information. I can create new ones if you have suggestions for which logs would be relevant.
80, 81, 3+81, then I hear something about MWB4. I'm not quite sure what to make of it.

By the way, the engine struggles to rev above 3800 RPM in 3rd and 4th gear, which is why I always shift before that point.

Best regards and thank you in advance.

Now I was too hasty when sending and forgot to include the link to the log; I promise to do better .

" /viewtopic.php?p=144654#144654 "

I hope this is correct now.



The boost pressure doesn't seem to match my display; I can definitely reach 1.8 bar, but then it drops back to 1.5 and settles at 1.2. Could the electronic sensor be defective and displaying incorrect values?

Greetings.

Hello Bubu.

Your log seems relatively unremarkable at first glance.

When you accelerate, there are slight overshoots up to 1.5 bar.
Normally, it should withstand a pressure of at least 1.0 bar.
That concludes the explanation of MWB 10.

Ich vermute deine LDA hat ein ähnliches Problem wie meine. She is "in the lead."
I don't find that so bad personally, because I know how much it is.

Unfortunately, I can't see much in the 8-megapixel image.
I'm missing the scale labeling that indicates which limit is currently active.

Perhaps the real experts here can chime in with their thoughts on that.

Quote:

I'm missing the scale labeling that indicates which limit is currently active.

Always driver - RPM - air.

It also looks inconspicuous.

Not RPM, but torque.
and what is limited is the lowest value.
You need to see this; it's not explicitly indicated which boundary is labeled "active."

Quote:

not RPM but torque,

There are ALL THREE torque limits, and the naming derives from how they are formed. One comes from the driver or accelerator pedal, one (which should be the main performance-limiting factor) comes from the RPM, and the last one comes from the measured air mass.

Therefore, the designation as it is usually found in the label and also in the repair manuals, namely "speed-dependent limiter," is quite accurate.

Quote:

and what limits it is the lowest value. You have to see this; it's not explicitly indicated which boundary is "active"

.

It seems the original poster (OP) was probably aware of this. However, since he logged the data without a label file, he simply didn't know which column represented what.

Hello and thank you very much for all the answers.

Let's start at the top: Mild overpressure up to 1.5 bar, which on the LDA quickly translates to seemingly dangerous, but actually harmless, pressures of 1.7-1.8 bar?
Or could it just be a sign that the VTG rod is starting to seize up? That would also explain the occasional power loss – it's rare, but it does happen.
I'm not talking about the emergency mode; I know that one. It usually happened afterwards, but it hasn't been happening for a while now.

MBB 10 and 8 are fine. Should I log another one, for example, values 4 and 11 (since they are frequently read, hence the idea)?

Does the log indicate whether the solenoid valve is functioning correctly? It seems that the rod itself might be a primary cause of the problem.

Regarding the torque/soot limitation, I'm not entirely clear on it yet. I promise to improve and will quickly familiarize myself with it, but for now: It seems okay so far, nothing alarming?

Here are a few more thoughts: During the test drive, the engine didn't quite reach the 4000 RPM mark in fourth gear. I stopped after a few seconds at 3800 RPM. In that high RPM range, it feels somewhat erratic and sluggish. With a slight adjustment (10 cents), I briefly managed to get it above that during acceleration (I wasn't paying attention, and I don't like revving it up that high).

Cold start is difficult, but it runs well when warm. The fuel injectors are probably still the original ones, but I'm not sure, and I doubt I'll be able to test them, especially with over 200,000 km on the clock (or maybe I can?).
I'm still hoping to find a common trigger that, if changed, would make all the problems disappear *g*.

I'll hold off on dealing with the other issues for now so I don't scare you all away right away. Right now, I'm going to investigate that clicking noise I hear when there's a change in load. I think I'll create a small overview later of everything I've already tried using the search function. I'm sure I'm overlooking some connections that would help narrow down the problem.

Greetings.

Quote:

I don't fully understand the torque/soot limitation yet.

He simply injects the smallest of the three values. However, this doesn't apply when he's performing idle speed or maximum RPM control.

Hello.

Okay, thank you. For the first time, I understand this. The lines aren't perfectly aligned, but what do they tell you? Is the LMM still okay? It looks strange to me (using KDataScope).


Today, the car ran smoothly on the track again, reaching 4000 RPM without any issues, which wasn't the case with the previous setup. So, I decided to check something:
"In the MWB 11 system, the baseline setting at 1400 rpm shows a pressure difference of approximately 60 mbar instead of the expected 100-150 mbar, which suggests (as I suspect) a stuck VTG valve. I still can't see it from above. On Monday, I can get onto a lift, but unfortunately, the conditions here are really poor (downtown, wet, cold, snow, parked on an incline)."


"With a water temperature of 65°C, I experienced a jerk and the engine almost stalled after 2 minutes of idling. There was no error message. This happened for the first time about two weeks ago while driving uphill (fully loaded) when trying to park. It simply wouldn't accept any throttle."
After that, error code 01268: "Quantity adjuster," showing "control difference interrupted" and "upper limit value interrupted." Is this definitely a defect? (I had briefly activated a performance tuning of about 10% while driving).

Sure, go ahead.
-Intake manifold pressure control differential interrupted.
- Intake air temperature sensor (G72): Open circuit/short circuit detected after positive voltage.
-Manifold pressure sensor G71: Open circuit/Short to ground.
- ABS data bus drive failure - Interrupted (cannot be cleared).

... were also included two weeks ago, but unfortunately, I hadn't saved them on my computer, otherwise I would have remembered to include them. They haven't reappeared since then.


"Additionally, there's a brief period of rough idling during cold starts, requiring 4-5 attempts to start in temperatures below -3°C."
Persistent exhaust smell inside the car, and clunking noises when shifting loads. When I manually turn the engine over, it squeaks and creaks under the air filter box – could this be related to the transmission bearing?

I performed the so-called "oil cap test," which is supposedly not very informative, and the result was: the cap bounced, and there were slight oil splatters on my hand. Just mentioning it.

"When it's cold, there's an occasional rattling sound coming from the diesel filter area. It's a strange noise. The filter has been in for 5,000 km, but it was purchased on eBay."

"There are vibrations coming from the drivetrain when accelerating forcefully. This is apparently normal if you push the torque too much when chipping the engine. However, it shouldn't happen with an unchipped ALH engine, considering its good tuning potential. Therefore, I suspect something might be broken."
It might indirectly be related to the clicking sound.
The workshop didn't find anything, even though we checked the drive shafts several times. I had to have the torque strut replaced, but that cost money and the problem is still there.

I'm sorry if I'm overwhelming you with a lot of problems right now, but I still hope that someone can quickly understand the connections and potentially help me out.

Greetings.

Hello,

Okay, I'd like to chime in again and report on what has happened recently. Since I've received such helpful assistance here, I'll also share the results with you.

Regarding charging pressure issues:

The typical behavior used to be in lower gears: When accelerating at full throttle, the LDA (Lambda sensor) reaches up to approximately 1.8 bar, and with a 10-point tuning adjustment, it can even reach 2 bar.

After approximately 900-1000 cycles using the large 100ml syringe, some progress should have been made. The gauge has now remained at a maximum of 1.5 bar for several weeks, dropping to around 0.9 bar, but then increases again to 1.1-1.2 bar as the speed increases.

I think I've been approaching this from the wrong angle all along, because it seems I don't have any massive overshoots that are set to a verschandeln 0.9 bar (standard) and then start rising again because the variable geometry turbine (VTG) isn't fully open.
In reality, the pressure seems to rise to approximately 1.3 bar, followed by a slight drop, eventually settling at around one (actual) bar.
Anyway, that seems to align with my LDA test results, which appear to be significantly off.
1.2 bar is approximately equal to 1 bar. The maximum pressure of 1.5 bar observed during overboost corresponds to (slightly less critical) 1.3 bar, and the previously displayed values of 1.7-1.8 bar, which have not reappeared, were likely my earlier logged values using VAGCom, around 1.5 bar.


For my part, I'm now driving much more relaxed, and everything just seems to make more sense compared to before.



Further changes:

Following Ulf's idea, I have modified a reversing light kit and added a relay that activates the VTG (Variable Torque Generator) every 1 second. A toggle switch in the glove compartment allows for quick activation, and I verschandeln the VTG at least once a week whenever circumstances allow. (Even when not under full load or during quiet highway driving, and even during warm-up phases, I do this.)

I'll definitely avoid upgrading the turbocharger for as long as possible.


I also examined the charge air cooler system. I extended and inspected the route from the EGR valve up to (and including) the intercooler. There were no oil leaks, just a lot of dust and dryness. If I remove the EGR valve now, will I damage any seals, or will I need new sealant?

There was estimated to be less than a shot glass full of oil in the LLK (low-pressure circulation system). Without stands to support the engine and a flat surface to work on, I can't remove the last piece leading to the turbocharger or inspect the charger shaft.



The jolts that used to occur during hard acceleration, which always caused unpleasant vibrations in the drivetrain, are now completely gone.
Of course, it was due to the relay 109. After just 5 minutes of driving, it was already getting warm.
The new relay cost me about 8 euros, and you can clearly see where the fault lies inside the old one.



Now I can only hope that the clicking sound is coming from the engine mount and not from the transmission/differential. If it doesn't cost significantly more than 30 euros at VW and similar places, I might buy it there, even though you can find them on eBay for as little as 10 euros (are they any good?). But I definitely won't pay more than 30 euros.


So far, thank you to everyone who has helped me. I will update you when I have solved another problem.

Best regards, Steffen.