Zu langsamer Ladedruckaufbau? | Posts 16+

donalexo wrote:

Earlier, I carefully read the technical article about replacing the timing belt on a TDI (as I hope). While reading, I realized that checking the timing is not as straightforward as I thought.

Hi Alex,

Do the pictures in the article match the timing belt side of your car? Mine looks quite different, in fact.

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With the TDI, you probably have to remove the valve cover, unfortunately, to access the notch on the camshaft where the adjustment tool should be inserted, right? Is this notch located on the side of the vacuum pump (why else would it be necessary to remove it during a timing belt change)? If so, does it also need to be removed when checking the timing? Is a visual inspection sufficient for checking the valve timing, or is the adjustment tool needed?

Well, in the TDI, the water pump impeller doesn't have a fixed position on the shaft; instead, it can be adjusted continuously thanks to the conical seat .
Therefore, the only reliable control is the bearing on the transmission side of the northwest (NW) direction.
Rainer wrote in his new post about the ZR replacement that removing the vacuum pump from the ZK (charger) might be sufficient.
But I haven't disassembled a motor like that before...

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If I have correctly interpreted the technical article, then theoretically I would not need to remove the timing belt cover to check the timing, but instead I would need to remove the valve cover to determine the camshaft position. On the transmission side, remove the rubber stopper and rotate the crankshaft until the OT mark is aligned. Is that correct?

Theoretically, knowing the precise position of the output shaft (through a viewing hole) and aligning the input shaft at the gearbox end using an alignment tool or similar allows for adjustment, and the transmission cover can remain in place.

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Can the valve cover gasket be reused (in terms of tightness!!), or should I get a replacement before doing this job? What torque should be used when tightening the valve cover screws?

I was able to continue using them without any problems on the AFN.
Torque -> for me, it's based on feeling .

A thousand thanks, Ulf!!!
Jetz muss ich Dir erst mal einen ganz großes Lob aussprechen. Deine Antworten auf meine Postings die flutschen ja nur so!! And technically, top-notch.

Actually, based on my current knowledge, I find the adjustment quite simple, as you only need to remove the rubber stopper to see the TDC mark, and additionally, you need to remove the vacuum pump to identify the camshaft timing mark. It actually sounds quite easy !

Can the position of the camshaft timing mark be accurately identified to detect a misalignment of one tooth?

Sure, you're welcome.

Regards,
Alex.

Hi Donaldexo...

I'm experiencing the exact same problem as you. However, I have a 1.0L engine. The turbocharger builds boost too late, there's not enough power, it feels like it's missing some Nm (Newton-meters)... and there's no soot.

I've already done it myself.

- Replaced the LMM (lambda measurement module) with a diode (which resulted in a slight improvement).
- Pump replaced (didn't improve performance, but eliminated the jerking/stuttering).
- AGR valve deactivated (metal part), and intake manifold cleaned (resulting in a slight improvement).
- Complete air system checked (no leaks).
- new nozzles (no noticeable difference)
- New air filter, new diesel filter (no difference).
- Performed test runs (all values were within acceptable limits except for boost pressure, LM = 255 ).

During the pump replacement, the Boschmann (mechanic) pointed out to me that my engine is making a 'gurgling noise' in one cylinder, likely due to valves or hydraulic lifters.
That's certainly a possibility, isn't it? A valve might not be sealing properly, causing the boost pressure to simply leak away.
However, there is nothing unusual to be observed in the idle speed control values (maximum value 0.4).
Does your engine sound 'different' in some way? It's hard to describe.
It appears that, in my case, the cylinder head (the one from the engine ) needs to be removed and reworked, with new valves, etc.
Has anyone had any experience with this?

Hello docSnydor,

How about doing a compression test before disassembling the entire engine?

Good idea, that's what I would do first too... I just wanted to explain to Donaldexo what else might be involved.

I'm personally just going to deal with the problem for now... It doesn't bother me too much, and I don't have a single euro to spare for the car right now, as I'm moving and need to buy furniture.

Hello everyone!
Today, on my way home from work, the subjective response of my charger improved noticeably. As if by a miracle, a thin sheet of spring steel had somehow become lodged in my engine compartment, nestled between two original AGR flange gaskets.
Right after starting the engine, the engine responded much better to the throttle and reacted very spontaneously to even the slightest throttle inputs.
Even when upshifting, the turbo lag (at least subjectively, as one can imagine a lot!) seemed to be less pronounced.
I am unable to provide information about the full-load performance, especially at engine speeds above 3000 RPM, as the road was too heavily trafficked.
I didn't feel an increase in performance (why would I?), but I only noticed a tendency towards more agile change-of-direction jumps. That's already a progress !
Hopefully, my illusions won't be shattered by irrefutable data!
As the next step, I will probably check the valve timing to be certain about that aspect.

@docSnydor:
You can imagine all sorts of things, but I also get the impression that the cylinder sounds a bit harsher than the others.
I believe this impression has already been present since the last timing belt replacement. Therefore: Check the timing first!
I find your theory about a leaky valve that bleeds off boost pressure to be unlikely, because, in my opinion, the LLRR value for that cylinder would have to be very high for that to be the case.
My LLR values are around +/- 0.2 to 0.3, so there aren't significant differences between the cylinders.

But, something else comes to mind: I think defective/leaky hydraulic lifters also lead to a loss of power at different engine speeds. However, my little engine only has 130,000 km on it. At that mileage, the lifters shouldn't be failing yet, right?

I will keep you updated!

Regards,
Alex.

donalexo wrote:

Can the alignment of the camshaft notch be recognized accurately enough to notice a misalignment of one tooth?

Hi Alex,

With approximately 40 teeth on the northwest wheel, each tooth corresponds to roughly 10 angular degrees.
You should be able to notice that even with a closer look.

If the technicians loosened the rear wheel nuts during the tire change, then "gradual" misalignments are naturally possible...

Hello everyone,
Here's another short, unfortunately sobering, progress report.
After my AGR (Acoustic Glide Retarder) system "failed" last week, I was completely convinced by the car's responsiveness, especially during the transition from coasting to acceleration. This improvement is undeniable.
Unfortunately, this change regarding the too-slow build-up of boost pressure didn't achieve anything. My logging today, performed on the exact same section of the track, showed the exact same engine speed and boost pressure curve (within tenths of a second)!

There's still a significantly large turbo lag at low RPM, and the maximum power output isn't reached until around 2500-2600 RPM.
I can now completely rule out a faulty EGR valve as the cause of the problem.

For safety, I logged the fuel injection adjustment again. It worked perfectly, and even at the rated speed, it doesn't reach the upper limit, meaning the duty cycle is approximately 88% (full throttle, 4000 RPM).

Well, I guess I'll have to keep searching (for things like valve timing, catalytic converter, wastegate...).

Wish me luck and give me good advice...

Regards,
Alex.

Hello TDI enthusiasts,
I have a request for you. If anyone of you has a TDI engine with a wastegate turbocharger and has the ability to do data logging (VAG-COM), I would greatly appreciate a set of measurements of the turbocharger pressure build-up as a comparison basis for my current problem.
Ideally, apply full throttle from approximately 1100 RPM in 3rd gear up to around 4300 RPM.
"Or, if anyone has logged this before on their Wastegate TDI, I would really appreciate it!"
The engine should, of course, be in good working order and should not exhibit any loss of power or other anomalies.

By the way: Which other Volkswagen models (besides the 1Z and AGR engines) actually have a turbocharger with a wastegate?
Just a suggestion: How about adding a row to the MKB table that indicates whether the turbocharger is a VTG (Variable Turbine Geometry) or a wastegate turbocharger?

Thank you for any support .

Regards,
Alex.

donalexo wrote:

By the way: Which other Volkswagen models (besides the 1Z and AGR engines) actually have a turbocharger with a wastegate? Just as a suggestion: How about adding a row to the MKB table that provides information about whether it is a VTG or a wastegate turbocharger?

Hello.

"Definitely, the AHU still has a wastegate turbocharger."

I would also find it interesting and useful to expand the motor data collection to include the charger type, as this would be helpful for providing relevant "advice" in the forum.

Unfortunately, I don't have a comprehensive or reliable collection of information on that topic.

Hello TDI experts!
Regarding my problem with the slow build-up of boost pressure, I noticed distinct pulsations in the exhaust flow today (at idle speed), which actually suggests that a severely constricted exhaust pipe is less likely to be the cause (e.g., a crumbling catalytic converter).

"In addition, I have thoroughly inspected my pneumatic hoses for the turbocharger control system again. I could not detect any anomalies. The data logging also shows that the boost pressure control system is working very well, because in the case of a wastegate turbocharger, the control system only needs to intervene if the pressure becomes too high. The fact that this only happens at a high engine speed does not change the correct function of the boost pressure control circuit."

The EGR valve was also temporarily deactivated using a spacer plate to rule out its influence.

I also rule out leaks in the area of the low-pressure coolant circuit or at the pressure lines, because otherwise the mass flow rate (MFR) signal would not drop at high engine speeds. If there were a leak, the value should actually continue to rise (and the turbocharger would overspin).

Meanwhile, I suspect there might be a leak in the wastegate valve, which is integrated into the turbocharger. What do you think of this theory?
The quasi-static boost pressure behavior of the engine also suggests this. For example, when driving uphill, where the engine is at full throttle and unable to significantly increase its RPM, my engine never reaches the target boost pressure at low RPMs (according to VAG-COM). This doesn't happen even after 20 or 30 seconds!
Above 2000 RPM, the target pressure is properly regulated. What experiences have you had with stationary, full-load conditions? After a long period, is the target pressure always achieved, even at very low RPMs, or is the target value unrealistic?

"I haven't been able to check my valve timing yet. I think it will be difficult because everything is mounted on top, making it hard to rotate the engine while it's stationary (to set it to Top Dead Center). Unfortunately, I don't have a pit or a lift, which would make it much easier to comfortably check the relative position of the camshaft and crankshaft."

If my suspicion about the wastegate valve turns out to be correct: Has anyone here ever cleaned or restored a wastegate valve on a turbocharger like this (by the way, it's a Garrett turbo)?
The AGR valve is located in such a difficult-to-reach position that it's almost impossible to get to. I think it might even be easier to access it from below than from above.

Thank you for your assistance.

Regards,
Alex.

donalexo wrote:

So far, I haven't been able to check my valve timing. I think it will be difficult because everything is mounted from the top to allow the engine to rotate while stationary (to set it to Top Dead Center). Unfortunately, I don't have a pit or a lift to comfortably check the relative position of the camshaft and crankshaft.

Hi Alex,

And what about using an open OT plug on the transmission, engaging 5th gear, and pushing the vehicle forward and backward on a level surface until the OT indicator appears in the window?

It works great on my tractor...

@ulf:
I'll give the "sliding technique" a try; it sounds tempting. Hopefully, it will be accurate enough to precisely align the motor with the top dead center (TDC) position.
But as the saying goes: "Experience is the best teacher!"

By the way: How is the vacuum pump sealed to the cylinder head? Can this seal be reused after the timing belt check, or is it a good idea to get a replacement beforehand?

Regards,
Alex.

Hi Donalexo,

What you are describing here is exactly the same thing that my 1Z is doing... It's true down to the smallest detail (even that it's very difficult to access the charger ).

'I'm also experiencing pulsating exhaust pressure. Could it really be due to a faulty exhaust? Everything after the catalytic converter is new on my car, so if it's something, it's probably the catalytic converter... But unfortunately, I doubt I'll ever be able to remove and replace it after 9 years and 225,000 km.'

Do you have an LDA? Try taking your foot off the gas at 2,500 RPM and then immediately putting it back on. I bet you'll instantly get full boost pressure, just like me...
I still believe that the cause of the problem (at least in my case) lies in the cylinder head...

donalexo wrote:

Meanwhile, I suspect there might be a leak in the wastegate valve, which is integrated into the turbocharger. What do you think of this theory? The quasi-static boost pressure behavior of the engine also suggests this. For example, when driving uphill, where the engine is at full throttle and unable to significantly increase its RPM, my engine never reaches the target boost pressure at low RPMs (according to VAG-COM). This doesn't happen even after 20 or 30 seconds! The target pressure is properly regulated only above 2000 1/min.

Hi Alex,

An improperly sealing wastegate could, in my opinion, completely and consistently explain the observed behavior.

AFAIK, a stiff loading shaft (e.g., due to oil sludge buildup after frequent overheating) could also be a factor.

Or a bottleneck in the intake manifold area, such as a partially blocked coolant line (due to something), a clogged air filter, or a blocked intake trumpet.

Hi Ulf,

Thank you for your expert advice.

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AFAIK, a stiff loading shaft (e.g., due to oil sludge buildup after frequent overheating) could also be a factor

.

I hope to be able to rule out this cause, as I generally take good care of my engine (and therefore the turbo), meaning I almost never drive it hard when it's cold, and I always let it idle for a few seconds before turning it off. Furthermore, I always use a full synthetic lubricant that is suitable for turbos and change it within the recommended intervals.
A carbonized wave would likely be a reason to completely replace the entire charger, right?

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Or a bottleneck in the intake manifold area, such as a (partially blocked by something) LLK, a blocked air filter, or a blocked intake trumpet.

I will proactively replace the filter element and disassemble the intake manifold to rule out any blockages or restrictions in that area.
A blockage in the lower lateral ventricle is also a good idea! Unfortunately, it seems a bit difficult and time-consuming to diagnose. Blockages in this area could actually only arise from the choroid plexus, right? Then, one would probably have to give the lower lateral ventricle a small flush with, for example, gasoline, to free it from deposits.

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A leaky wastegate could, in my opinion, completely and consistently explain the behavior.

I think we agree on that. Do you know of any specific cases where this has happened? Could the leak in the wastegate be fixed with simple methods?
Perhaps the diaphragm in the wastegate control system is faulty, for example, due to excessive internal friction, which prevents the spring from pushing the diaphragm all the way back? Have there been similar cases before?
Or the actuation rod has become lodged in the guide and is preventing the end stop from engaging.

Finally, a question about the ongoing topic of checking valve timing. When disassembling the vacuum pump, is the seal to the cylinder head damaged, or can it be reused without any problems?

Sure, here's the translation:

"Thank you in advance."

Regards,
Alex.