ASZ Engine: Sudden Power Loss - Troubleshooting Guide

Good evening everyone!


That's the end of the vacation...


My engine is having problems again.
A few weeks ago, I reported on extreme Russians in this post here.

Today, it happened again: the engine suddenly lost power.
Even restarting the engine didn't help.
Previously, this problem was always resolved immediately.

Here is the engine and error description:

130 hp ASZ PD TDI engine, manufactured in December 2001.
65,000 km
Chip tuning for 50,000 km.

New replacement air filter.
Half a tank full.
Rainy weather.
AGR disconnected.


From the point where the turbocharger should actually start to noticeably engage (approximately 2000 RPM), nothing happens.
The engine continues to rev up slowly when the accelerator is fully pressed, but without producing any additional power, and it makes a very rough sound while doing so.
If I ease off the accelerator pedal (to about a quarter of full throttle), it noticeably pulls uphill with more power.
It feels the same as always down there.
V/Max is 130 km/h.
The Russian car is completely gone, regardless of the pedal position and engine speed range.


It feels like the turbocharger isn't building any boost pressure at all.
The familiar turbo whistle is still audible, but the different whistling sounds within the RPM range have changed.

Before, starting around 1300 RPM up to about 2000 RPM, one could hear an increasing 'Oohhh' sound.
Above 2200 RPM (where the turbocharger boost became noticeable, and it had recently been surging strongly for short periods), the whistling sound changed to a turbine-like roar, which was no longer audible at higher speeds.

When the engine was turned off after normal operation, a noise resembling that of a 'turbine winding down' could be heard (likely the turbocharger's after-run).

Now, below 2000 RPM, I can't hear the turbo at all, and from 2000 to around 2500 RPM, I hear this 'Uiiiihhhh' sound.
The turbine-like noise is no longer audible; I can only hear the hammering sound now.
When parking, there is no noticeable turbo lag to be heard.


I then reconnected the AGR valve, repeatedly shook the boost pressure control valve (the one with the white cap) with a screwdriver, detached the small hose that goes to the air filter housing, and sucked on it.
It was then that a clicking sound from a membrane could be heard.


It didn't bring about any improvement whatsoever.

After approximately 5 hours, I tried to start the car again, but it wouldn't start.
After two attempts at playing the organ, it suddenly started working.

Then I disconnected the mass airflow sensor connector – there was absolutely no difference noticeable.
Okay, so the mass airflow sensor is reconnected, but there's still no difference.

Is that an indication that the engine is in a limp mode?
If I disconnect the LMM, it should theoretically do that.
But will any boost pressure be generated at all then?

I know I'm not exactly impressing anyone with my diagnostic data here, but the VW dealership was already closed, and I didn't want to ruin the whole day for my annoying friend.



Tomorrow, I'm going to take my car to Volkswagen and have them read the error codes.
Perhaps we can already see something there.
A question for clarification:
If the turbocharger were broken, wouldn't the car produce a lot of smoke because the fuel mixture would be too rich?


Greetings from my vacation (which will probably, unfortunately, be spent in Berlin ).

Jay_Dee wrote:

Tomorrow, I'm going to take my car to Volkswagen and have them read the error codes. Perhaps you can already recognize something there.

Yes, maybe -> hopefully!

Quote:

A question about understanding: If the turbocharger were broken, then the car would surely smoke a lot because the mixture would be too rich, right?

No, that's incorrect: In that case, the mass airflow sensor (MAF) would report less air intake, which would cause the fuel injection amount to be reduced in a way that prevents soot formation.

Without measurements, nothing will work! So, please provide the measurement data.

To me, it sounds like a faulty mass airflow sensor (MAF). I've experienced something similar multiple times. However, this is purely speculative and may not be the actual problem. It could also be a leak in the intake system, a stuck variable turbo geometry (VTG), or something else entirely.

Please review the relevant technical articles regarding LMM (Lambda Measuring Module) and troubleshooting performance loss, as well as the interaction between boost pressure, air mass, fuel injection volume, and power output. From what I understand, there are some deficiencies in this area.

A friend of mine had the exact same problem with his A4 PD. It turned out that something was wrong with the 'valve' that regulates the turbo boost pressure. Unfortunately, I don't know any more details because it happened quite a while ago.

To me, it sounds like a faulty mass airflow sensor (MAF). I've experienced something similar multiple times. However, this is purely speculative and may not be the actual problem.


I would initially make that diagnosis remotely, but as I said, we need to get some measurements.


However, it could also be a leak in the charge air duct, a stuck VTG (variable turbine geometry), or something else entirely.


I would rule those out for now, because a leak in the charge air system would cause it to smoke, and a stuck variable geometry turbo (VTG) usually becomes noticeable under load due to jerking or hesitation.

Regards,
Best regards,
Sincerely,
(or simply)
Cheers,

@troubleshooter

However, based on his initial post, there are indications of a potential vacuum leak and/or an air leak in the charge air system.


When I accelerate from lower RPMs, the car makes a very noticeable 'rushting' sound starting around 1800 RPM, which is about when the turbocharger starts to kick in.
At higher speeds (approximately 2500 RPM), the engine starts to misfire.
The Russian car is so powerful that cars driving behind me immediately increase the distance and start using their headlights aggressively.

Oops.

@joergs --> Sorry, I completely missed that.

'You're right, it sounds like a charge air leak. In my Golf IV, the rubber hose at the bottom of the intercooler often fails. However, the power loss isn't too drastic in that case, but it is noticeable.'

Regards,
Best regards,
Sincerely,
(or simply)
Cheers,

Oops.

@joergs --> Sorry, I completely missed that.



It's okay...

Hello!


As I said, the smoking issue is completely gone.
TS, what do you mean by 'Gimmuschlauch'?
Do you mean a rubber hose, or am I once again completely misunderstanding something?

The hose connecting the coolant reservoir to the intake manifold keeps slipping off (at the point where it connects to that plastic hose).
It's not really possible to tell if it will leak as a result, but it seems to be hanging loose there.
It doesn't really seem like a serious relationship.

Is there no other way to confirm this?




This morning, I went to Volkswagen to have the error codes read from the car's computer.


The engine wouldn't start again this morning.
It only started on the second attempt, and then it turned on immediately.


The following errors appeared during the diagnostic scan:
(I don't remember the exact wording because the diagnostic device wasn't connected to a printer.)

Mass airflow sensor, intermittent short circuit to ground.

G71 Intake manifold pressure, short circuit to ground, or open circuit.



Some time ago, I had the memory read out, and during that process, the sensor G71 was already showing unusual behavior, although it was only sporadic at that time.
Now the error is permanently present.


That's probably the devil's work, and it explains why the car won't start at all.
Tomorrow, the pressure regulator should be in the warehouse, and then I'll try installing it myself.
However, I still have one question about the sensor.
It was a bit unclear when ordering parts from the sales department.
Is the sensor G71 the component located in the pressure pipe just before the intercooler?
Or is this one of the sensors that are attached to the engine's spray bar?



Unfortunately, a test drive wasn't possible. I think it will only make sense to do one again after I replace the boost pressure sensor.



Not quite as desperate greetings...

Jay_Dee wrote:

It was a little unclear when ordering parts from the sales department. Is the sensor G71 the component located in the pressure pipe just before the intercooler? Or is that one of the sensors that are attached to the motor's spray wall?

Sensors on the engine's spray wall?
What should they be (function)?

In the Programmable Drive (PD) units that I am familiar with, G71 is combined with G72 in a single housing (charge pressure + low-temperature control).
In the direction of flow, it is located behind, not in front of, the air conditioning unit.

I'm not sure which 'sensors' the man from Volkswagen was referring to either.
Perhaps he was confusing it with something like the boost pressure control valve?
That often depends on the circumstances.


Yes, the LLT should be located after the LLK .
Okay, I'll see if I can get to it from below tomorrow.
Okay, remove the underbody protection and grab the flashlight.

Today I picked up the boost pressure sensor (G71) from Volkswagen. I drove to my workshop with a measly 40 horsepower and started the repair there.
Unfortunately, the sensor is located on top of the front axle assembly, which means the front fender liners need to be removed.
I also removed the headlight and detached the locking mechanism on the right side.
That's how I managed to get quite close to the sensor.
You can safely forget about disassembling it without a Phillips head screwdriver.
When I held the sensor in my hand, it quickly became clear why it had stopped working.
He had a large tear in the middle. It probably wasn't very pressure-resistant .
However, the sensor was not the only component that proved to be reliable.
The intercooler charge air hose looked very old, so I took a closer look at it.
A piece of the rubber seal was sticking out from the clutch.
I removed the liquid cooling system, repaired the damaged area, installed the new sensor, and reassembled everything.

The engine started, I pressed the accelerator, and a familiar turbo whistle could be heard.

G71 was the solution to the puzzle.
A leaky turbocharger boost hose was the cause of the problem described in the post linked above.
Russ is no longer visible while accelerating!


Thank you for the comments...

Do you think it was a manufacturing error with the LL hose? I remember noticing something similar on my brand new Golf – the clip at the connection point between the LL pipe and the intake manifold was "misaligned." Or is it simply due to the natural aging process, as much as that applies in this case?

Good question.
It has nothing to do with the aging process.
I think it's more likely that the boost pressure is simply too high for these rubber couplings.
The sealing ring was torn and a small piece of it was protruding from the bottom of the clutch.
It's possible that it wasn't assembled correctly during the repair back then either.
The excessive smoking that occurred just before the turbo engaged is definitely gone now.
Now it only smokes when you step on the pin.

Have a nice evening...