AXR PD: Charger/Backup Power Issues

Hello,

First of all, I'm happy to be registered here with you .

Okay, now to my problem... right off the bat, I'm not a mechanic or anything like that, and I can't read the error codes myself.

I drive a Volkswagen Golf 4 with the aforementioned AXR pump-injector engine, manufactured in March 2002, with an output of 74 kW. The engine has approximately 40,000 kilometers on it.

So far, so good - until now .

'Recently, I've been experiencing a problem where the engine suddenly goes into limp mode while accelerating on the highway (and only there - everything is fine in the city). There's absolutely no power.'
- Of course, after a short pause and by turning it off and on again, it works smoothly again.

Okay, since the engine has been exhibiting poor throttle response during cold starts lately (in the first 1-2 minutes, I have to really push the turbo to get it above 2000 RPM), I immediately suspected the mass airflow sensor (MAF) and went to my trusted mechanic hoping he would replace the MAF and that would be the end of it...

But I was wrong... the result surprised me quite a bit... allegedly, the turbocharger is defective (allegedly, it's producing overpressure and causing the car to go into limp mode), and to be 100% sure, they want to do a 'turbocharger comparison test' (2 people will drive my car on the highway until it goes into limp mode - AMAZING ).

I thought to myself, 'Never mind,' and took my car again.

Last weekend, I was on the highway again and observed it happening once more – indeed, it went into emergency mode twice.

First time on the way there - shortly after starting... I accelerated from 60 to above in 4th gear (out of 60), but it stopped at 80 - EMERGENCY MODE.

2. Approximately 1 hour later, while accelerating in 5th gear from 80 upwards, the car suddenly stopped at 140 .

After that, on that day I drove another approximately 200 kilometers, and the next day about 350 kilometers, and that WITHOUT any problems whatsoever... no warning lights, nothing at all... not even under full load and at around 190 km/h.

**************************************************************

What could it possibly be? I've read a lot of posts here, but nothing seems to quite fit.

I was still thinking it might be a misaligned VTG vane, a defect in the turbocharger's vacuum system, or a faulty solenoid valve...

However, it doesn't quite seem to fit the picture – after all, it's only an occasional issue that doesn't occur in the city at all, and apparently only manifests when accelerating in the higher gears.

'Shouldn't a defect like the one mentioned be reproducible and always occur? Either something is broken in the vacuum system, or it isn't... Similarly, if the VTG adjustment mechanism is stuck, it doesn't just jam up occasionally, does it?'

Can the VTG (Variable Turbine Geometry) adjustment mechanism be cleaned without removing the turbocharger?

Please provide the text you would like me to translate from German to English. I will then give you only the translation, without any explanations.
Sorry, I don't know how to proceed - I really can't imagine a charger defect (my wallet, by the way, also doesn't work ).

Okay, thank you in advance...

0815user wrote:

allegedly, the turbocharger is defective (allegedly, it produces overpressure and triggers the emergency mode)

Well, as long as you can't read the error codes yourself, you're naturally at the mercy of the workshop's claims, with all the potential consequences that entails -> $$$$$$.

Otherwise, there are definitely tips in the technical articles that allow you to at least partially check chargers and similar devices without digital support.

Hmm,

Do you mean...?

Symptoms: Idling instability in PD engines, occasionally accompanied by misfires during driving and/or a lack of power.
Common causes: Clogged diesel filter.
Tests: Diesel filter can be temporarily replaced with a new one for testing purposes.
Troubleshooting by: Installing a new/verschandeln diesel filter.

Well, that would be something... but I don't think so, because the car was at its first inspection with VW at the end of January, and I assume they would have noticed something like that .

Or rather:

Symptoms: Intermittent or constant lack of power in some or all engine speed ranges, occasionally 'acceleration dips' in specific engine speed ranges.
Full power is sometimes only available for a short time after the engine restarts or when you release the accelerator.
Occasionally, error messages such as 'Intake manifold pressure control differential,' 'Forced induction pressure regulation exceeded limit,' or similar appear.
Boost pressure indicator (if available) shows unusual/incorrect values.
Common causes: Faulty boost pressure control or turbocharger.
Exams:
-> Read boost pressure using the diagnostic system (if no Low-Pressure Differential Adapter is present).
-> Check the charging system's coolant hoses for proper seating, kinks, soft spots (!!), and leaks.
-> Check the charge control mechanism (wastegate/variable geometry turbocharger).
-> Try replacing the turbocharger wastegate solenoid (with VTG chargers, it's often possible to replace it with the 'original' EGR solenoid, but this should not be considered a permanent solution due to the detailed differences between the valves).
-> Remove the intake pipe to the turbocharger and check the compressor wheel for smooth rotation and proper bearing alignment. When tilted and rotated, the turbine should not rub against anything.
Troubleshooting by: Replacing defective and suspicious hose sections or the turbocharger solenoid valve, ensuring proper function of the VTG mechanism, installing a larger VTG charge air cooler, and if necessary, replacing the entire turbocharger.

To troubleshoot overboost conditions in a VTG turbocharger, you can disconnect the vacuum hose from the control valve and, during full-throttle acceleration to at least 4000 rpm, observe the boost pressure. Some increase in pressure is normal during this process, but the normal maximum boost pressure should not be exceeded!
If so, the possible causes are:
1) Membrane dose clogged due to an internal defect (partially) -> Replace the dose.
2) Movement of the steering vanes in the loader is partially blocked due to Russian sediment buildup -> clear the blockage.
3) The diverter mechanism is jammed due to overheating (excessive tuning) -> save up for a new turbocharger.
4) VTG rod set too short -> extend in increments of half turns.

If the boost pressure remains below the normal maximum value even without active turbocharger control, the fault lies within the vacuum system (hoses / vacuum pump / solenoid valve / cables / engine computer).

It would certainly be possible... especially since it's alleged that there was an error in the fault memory, and that error didn't disappear after restarts...

BUT it says 'within certain speed ranges'... that's exactly where my problem lies - I simply can't pinpoint it to a specific range!

Could it be possible that there's a fault with the engine control unit (ECU), and the electronics are just malfunctioning intermittently, misreading values, and therefore triggering the limp-home mode? Has anyone experienced something like this before?

What about these so-called 'overshoots' – could they occasionally trigger the emergency stop?

Does anyone have any experience with an AXR-PD?

...Well, questions upon questions... I'm going to study some more technical articles now .

0815user wrote:

BUT it says "within certain speed ranges"... that's exactly my problem - I simply can't pinpoint it to a specific range!

First of all: it's great that you're browsing and finding things here (unfortunately, this isn't always the case for many new users).

Secondly, the specific symptoms don't necessarily have to perfectly match every single case. I would definitely start by using the troubleshooting approach mentioned earlier...

Quote:

Is it possible to verschandeln the VTG adjustment mechanism somehow WITHOUT removing the turbocharger?

Hi,

Theoretically: yes. Practically, probably not. If you can access all the necessary bolts to separate the impeller housing (gray cast iron) from the rest of the compressor...
Disconnect the oil lines beforehand.
The problem is that you can't really get close enough, and if the loader gets stuck or tilts downwards during removal, the wheel is quickly damaged. That's it; at those speeds, even the slightest imbalance puts a lot of stress on the shaft.
Therefore, I would definitely completely remove the charger so that I can thoroughly verschandeln it on a workbench at my leisure.
The retaining screw for the compressor impeller must not be loosened (and is not needed to be loosened).

Of course, this is only if your VTG adjustment is actually malfunctioning. Therefore, I would say that reading the error codes is mandatory before doing any further modifications.
The likelihood of performing pointless and time-consuming DIY activities (with the added risk of breaking something) is not worth the effort required to read the error codes.

Best regards, Rainer.

Okay, thank you for the answers so far. I will soon go to a different 'friendly' mechanic and have them read the error codes again using Xtra...

I'll get back to you here again later.

P.S.: However, I suspect something like 'sporadic intake manifold control differential.'

Here's another tip: Don't wait too long to read the error codes, as sporadic errors may be cleared after several trouble-free trips.

0815user wrote:

Does anyone have any experience with an AXR - PD?

Yes!

The approach you chose should be the correct one (stuck VTG).

@0815
Why would a faulty solenoid valve and the intermittent nature of the error exclude each other? In my experience, they often go hand in hand.
Other options have already been mentioned to some extent...

Well, I don't know it for 100%, but a defect should probably occur relatively frequently to always... my problem only happens on the highway, and even then, only in about 10% of cases .

I don't have a valid REASON.

If it's that rare, a sporadically malfunctioning solenoid valve is not unlikely. These parts can be quite temperamental.
"For 30 euros, you can try it out. Even if it turns out not to be the problem in the end, you at least have a spare valve, which is never a bad thing (I've been stranded on trips multiple times with a faulty N75). In case of emergency, you can quickly replace it and don't have to rely on workshops. The last time, the N75 failed 500 km after buying the car (first occasional errors, then constant). But I've also had cases where it sporadically caused control errors for years (ranging from 5 times a day to not at all for 3 months). Once it was the N75, and once it really was the turbocharger."

Regards,

Olaf.

@ Olaf

No, the N75 only costs 30 euros for the wastegate (and even then, it's referred to as just a solenoid valve).
For VTG systems, these are pressure transducers and cost between 100 and 200 euros!

Okay, please provide the German text you would like me to translate into English. I will only provide the translation.

Great, someone once told me they were supposedly the same... If the VTG uses a different valve, then I'm not sure how applicable my experiences are.

See you then.

Olaf.

DO you still have the 3-cylinder engine with the single valve?

Be glad that later on, with the 3-cylinder engines, all air pressure regulation was integrated into a single block; otherwise, it would become very expensive.

Wastegate turbochargers are pressure-regulated, while VTGS systems use vacuum (similar to how our EGR system works).

A VTG engine therefore has two similar, but not identical, valves (one for EGR and one for VTG).

We have a magnetic solenoid valve for the turbocharger and a pressure sensor for the EGR system.

Greetings.
Okay, please provide the German text you would like me to translate into English. I will only provide the translation.

It's already clear that the wastegate operates under pressure. That's why I was always surprised that they should be the same valves. Well, a quick look at the documentation would have been enough.
"Since when was that changed? My 2000 model has a combined vacuum component (I have no idea how it actually works) for the EGR and bypass valve, and the well-known N75 for turbocharger pressure control. A friend of mine's car (year 2002) looks exactly the same."
I had to replace the original N75 valve in both of my Lupos because they were defective. Once, my tuner paid for it, and once, VW paid for it. A while ago, I bought a spare valve cheaply on eBay so that I could replace it if needed. If the valves in the newer AMFs can't be replaced individually, that would be an argument against them. I've always been annoyed because my timing belt needs to be changed much sooner.

Regards,

Olaf.

Hmm.

Since when was that changed? My 2000 model has a special combination vacuum part (I have no idea how it really works) for the EGR and throttle valve, and the well-known N75 for turbo boost control. A friend of mine's car (year 2002) looks exactly the same.

I also have a 2002 model... But I guess your friend didn't have a PD engine, did he?

@dieselmartin - What about:

> Try replacing the charge pressure solenoid valve (with VTG chargers, it is often possible to replace it with the 'original' EGR solenoid valve, but this should not be a permanent solution due to the detailed differences between the valves)

Und überhaupt...ist doch klar...aus N75 mach wir jetzt nen Druckwandler & dann nehmen wir eben den 5 fachen Preis - typ. VW, hold on...

Well, whatever... I might consider it if it were 30 euros, but at 100-200 euros, I'd only buy it on a whim... no way.

I'm going to the 'Friendly' (likely a repair shop) tomorrow, and hopefully I'll at least get a fault code... Maybe then you'll have more ideas...

'Der schnelle braune Fuchs springt über den faulen Hund.'
It's somehow difficult not to spend a significant amount of money on repairing an intermittent fault that is annoying, but only occurs 1-2 times a month... - What's the worst that could happen if the charger is defective; I can always have it replaced .

By the way, is it actually normal that Volkswagen wants to replace the turbocharger immediately, without even looking at or replacing any other parts first?

It feels like they just want my money . After all, I'm already 4 months outside of the warranty period - WOW }.