Boost Issues Solved: Troubleshooting & Fixes

Hello!

Since my Polo 1.4 TDI AMF is no longer delivering its full power, I logged the boost pressure curve.

The turbo boost pressure is always too low, or it kicks in too late.
Could it be due to the N75 valve?

I hope you can help me solve the problem using the diagram.

http://www.keepmyfile.com/image/2f1282778424

and the complete xls file containing the material numbers 003, 008, and 011.

http://www.keepmyfile.com/download/c5645e778445

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

"Best regards,
eskomo"

Please read the measured values in display group 010 and 011.
from... 3rd gear at 3000 RPM... to see what the boost pressure is.

Hello wob-in,

I've created a new chart (with an engine speed of 3000 RPM, 3rd gear).

Initially, you can clearly see the noticeable delay in pressure buildup when accelerating or shifting gears.

At 3000 RPM, the pressure is approximately 150 mbar too low.

Starting it is really quite tedious... it has no power.

Printing progress:
http://gload.de/preview.php?file=cebee818ee1b26280dcf56b29.jpg


MWB 10 and 11 as xls files:
http://gload.de/files/a133b346d3d27c50e104c9b27.xls


"At idle, the absolute boost pressure is 898 mbar (which is even below the ambient pressure of 908 mbar)... How is that possible?"


What do you think about that?


Okay, what's the actual difference between "Manifold Pressure" in the MWB10 and "Actual MAP" in the MWB11?

best regards,
eskomo

Hello,

It's perfectly clear that you have a lower pressure in the intake manifold at idle compared to the ambient pressure.
The turbocharger is not reaching a high enough RPM to generate positive pressure on the intake side. Consequently, the engine's intake pressure is higher than the turbocharger's boost pressure, and you are measuring a vacuum.

Your turbocharger is regulating, which is clearly noticeable. However, this regulation is very slow. It only reaches the desired pressure with overshoot.
In my opinion, it's more likely related to the mechanical aspect. So, it could be a 'stuck' actuator or a leak in the vacuum line leading to the actuator.
Perhaps there's a problem with the turbocharger itself, such as a stuck wastegate. Do you often drive with partial throttle and frequently accelerate from low RPMs?

Best regards, Jochen.

Hi!
Sure, are you certain that your boost pressure system is airtight? In your logs, the duty cycle of the solenoid valve is almost always at its maximum boost pressure setting, yet the target pressure is not being reached, even at high engine speeds. Perhaps investigate that possibility, or also consider a stuck-open EGR valve. Oil traces on the intercooler or the hoses can be a telltale sign.

Best regards,
Dirk.

The problem is more pronounced when the engine is still cold, so I don't think there's a leak.
I suspect it might be related to the charging coil (perhaps it's stiff?).
After the last oil change, I had great responsiveness for about a week.
According to the workshop, nothing was done other than an oil change.

It looks like he'll probably need to take it to the workshop. I hope I don't need to buy a new loader.

So, if you're not willing to use the suggested troubleshooting steps or search for solutions, then you'll probably have to take it to a repair shop, right? Have fun.

Hello brezelmann01,

I had hoped that it might be something minor that I could fix myself.

The engine compartment is so tightly packed that you can't really access anything without removing several parts (you can barely even see the turbocharger).

I don't think it's an open AGR system (because there's no increased soot emissions).
And checking the intercooler piping for leaks is also difficult (I couldn't see any leaks - but if it's just a small crack, I'll never find it).

Thank you for the tips!


ls, eskomo

Hi!
As you can see, I also have a Polo TDI, and it's definitely possible to examine the engine compartment more closely. It's not really a problem with a flashlight – and if necessary, you can always remove the lower splash guard. You can even see a bit of the intercooler from the front and back (at least in my 6NF). I'm actually surprised that no increased soot emissions can be detected. Likewise, it's surprising that the engine doesn't go into limp mode.
Well, it would still be nice if you could share the solution with us.

See you.
Dirk.

Hello!

Unfortunately, the workshop wasn't much help - they said the turbocharger boost pressure is within the "normal range"... those must be real experts!

Well, maybe I'll be able to announce the solution to the problem sometime after all...

Hi and thanks again.

If it was better after the oil change and is now worse again, it's possible that the shaft isn't being properly lubricated with older oil.
That's quite a stretch to suggest that the quality of the oil changes so significantly due to the presence of rust, to the point where it restricts the viscosity.
Furthermore, this would mean that the oil line or the pump itself would have to be clogged with carbon deposits within the oil circuit, which would obstruct the oil flow.
That would be bad, because the charger wouldn't last long.
And with too little oil, the loader would also become noisy.

I think, like my predecessors, that there's a leak somewhere in the system, which is why the loader takes so long to reach the required pressure.

By the way, be careful, the loader will then be running at an overspeed.

Best regards, Jochen.

Hi,

I also thought that the oil couldn't lose that much lubricating ability within a week.
Perhaps the workshop accidentally shifted a hose during the oil change, which temporarily sealed it for a week - although that's also unlikely, right?

As I mentioned, the problem is not quite as pronounced when the engine is warm.

"What's the easiest way to find a potential leak? I think it's probably not that easy without special tools – it's probably just a small hole, otherwise I think I would have noticed it already."

eskomo wrote:

What's the easiest way to find a potential leak? I think it's probably not that easy without special tools - it's probably just a small hole, otherwise I think I would have noticed it already.

Brezelmann already wrote about this above:

Quote:

Oil traces on the LLK (low-level connector) or the hose are revealing.

Technical articles and search functions can also lead there .

Hi!

Here is the solution to the problem:

I went back to the workshop again. They welded the resonator, and now I have full power again.

Hi!