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Hello everyone,

Last night, while driving uphill, I noticed a bang coming from the engine compartment. It sounded like a hose had burst off a pipe. Immediately, the speed decreased – there was a loss of power. This morning, I couldn't find any disconnected hoses. The engine starts normally and doesn't make any unusual noises.

The diagnosis states:

- 17911 45F7 P1503 Load signal from generator terminal DF, implausible signal.
- 19559 4C67 P3103 engine, intake manifold flap V157 defective.
- 17965 462D P1557 Turbocharger pressure regulation: Limit exceeded.

Does the exceeding of the specified range stem from a malfunction of the V157 component?
However, none of these error messages suggest that there was a sudden jolt or hiccup, do they?

I am grateful for any suggestions!

Normally, a loud bang is often caused by a loose or burst boost pressure hose. In the case of the Polo, the hose that runs from the turbocharger to the intercooler at the bottom is particularly prone to this issue, either due to bursting (cracking) or the retaining clip breaking off at the connection points to the next pipe.

Please check all the intercooler pipes for oil leaks. If it's cracked, you'll be able to see it clearly. However, if the intercooler duct is open, the engine sound will also become noticeably duller/more rumbling.

One of the error messages "boost pressure control - limit exceeded" already indicates a leak in the charge air system. The errors occur when the engine is trying to achieve the desired boost pressure, but it cannot be reached by the boost pressure sensor because air is escaping.

Just double-checked everything again – no leaks or loose hoses visible. During the test drive just now, everything was normal again... Self-healing?

This morning, the error was found in the workshop. Luckily, it was only a thin hose that had broken - the mechanic knew better where to look .

Just now, it happened again. Overtaking maneuver, everything was fine up to about 3500 rpm in 4th gear, then suddenly no power at all. (Emergency mode?) After restarting the system, everything went back to normal. However, I think I've found the culprit now. (See picture)
What function did this defective hose serve?

[edit] Let's take a closer look at image 2 and add some more details.

Replacement part for the boost pressure control system of a turbocharger with a wastegate.

Should I be worried about the oil on the hose?

"What would worry me more is the frequency of defects. Have you ever logged the boost pressure?"

What does "defekthäufigkeit" mean? Did you notice the "mechanic's" "troubleshooting" in Image 2? The hose simply tore again at the second weak point, higher up.
I'm guessing that the damage was caused by a weasel.

Failure rate = a component fails twice within approximately one week.

"Twice the same damaged component... He should have replaced the first hose on the pressure relief valve for 5-10 euros and installed two new clamps. The clamps look exactly like the entire hose, and no one has touched them."

Instead of that, he simply wrapped the damaged hose with tape and probably ignored the cracks in the other hose further up, leading to the N75 valve. I wonder where we are heading if workshops operate like this... It doesn't take any longer than 10 minutes; it's just incredibly careless.

I think that both(!) hoses were corroded. The picture also shows this in the area of oil contamination on the hose. What should the boost pressure be for the hose to burst if it is in good condition? 12 bar?

In my opinion, it tore off as a consequence of structural damage.

matthiasTDI96 wrote:

Failure rate = a component fails two times within approximately one week.

"They are different hoses... or are you referring to the turbo with 'part'?"
I'm going to record the boost pressure now and then upload the results here.

Edit:

Deus Violentia wrote:

Twice the same, damaged component... He should have replaced the first hose on the pressure relief valve for 5-10€ and installed two new clamps. The clamps look exactly like the entire hose; nobody has touched them. Instead of that, he simply wrapped the damaged hose with tape and probably ignored the cracks in the other hose further up, which makes me wonder where we are now if workshops operate like this... It doesn't take any longer than 10 minutes; these people are truly clueless.

The first time, a new piece of hose was already installed - connected with plastic connectors. The tape is just an additional layer around it. I don't want to judge the quality of the work right now .
For me, the only question now is whether it's still worth collecting data on boost pressure. Could the turbocharger have been damaged due to the faulty hoses?

I'm referring to your intercooler system. It's possible that everything is rotten and old. There could also be pre-existing damage, which I can't assess. What I see in the photo looks like very sloppy workmanship. Therefore, I would only advise the person who posted the original message to carefully inspect their entire engine bay, replace any damaged parts, and then, just out of curiosity, create a log to see if there are any other potential issues.

We always write in parallel . I'm going to do a log run now and post the results.

Hello,

Here's the log file. I hope I logged the correct sections.

Okay, I'm not going to look at that. The reason is: We've talked about what a proper log should look like approximately 1457 times. It only makes sense to analyze something if it conforms to those standards.

"Third gear, full throttle from just over 1000 RPM to the maximum... this is one of the main points being made in all the posts because: it's a fairly dynamic system, and if you're constantly adjusting the accelerator with your right foot, the car will react accordingly. Therefore, aiming for 100% throttle on the gas pedal in a higher gear is ideal to see how the engine control unit (ECU) starts to regulate the turbo boost."