Sinkende Leistung und steigender Verbrauch

Golf VI, ALH engine, 105,000 km, only used for long distances.


Hello everyone,

Here's a brief account of my frustrating experiences with this topic.
'Decreasing performance and increasing consumption.'

I'm experiencing the exact same symptoms as 'mhernach' did. In addition, I'm also experiencing a surging acceleration around 3000 RPM and under heavy load.

Of course, I thoroughly researched this forum before getting started.

1. Vacuum hoses checked - all OK. - No success.
2. For safety reasons, the diesel filter was replaced after only 40,000 miles.
- 26€
3. Pneumatic valves were swapped, but without success.
4. To get more 'imput' (likely referring to input or data), I bought a 'Golf 4 TDI repair manual.'
- €23

5. Out of sheer desperation, during a VAG diagnostic test and compression test.
assigned, the new LMM brought a slight improvement, and therefore...
6. Purchased a new LMM (likely a mass airflow meter) - only slight improvement - €324.
7. Instantaneous fuel tank ventilation - Air bubble formation. Diesel hose disconnected.
8. Studied the repair manual, ordered gaskets, removed the EGR valve.
- Bullseye €12

There was so much carbon buildup in the intake manifold (6mm behind the AGR valve, and 2mm directly on the cylinder head all around) that I cleaned it by filling it with gasoline in my father-in-law's fireplace and burning it out. It sputtered and hissed like a burning oil well for over an hour. Afterwards, I was able to easily knock out the remaining residue.
The EGR valve was completely clogged with carbon deposits, so it couldn't close properly and was constantly leaking exhaust gases.
UNFORTUNATELY, during installation, loose pieces of metal debris clogged the AGR valve, and it is guaranteed to no longer cause any problems in the future.

The first test drive made me very happy. The performance is like it used to be, the engine response is much better, and the fuel consumption has decreased by almost 1 liter.

What can we learn from this?
At VAG (Volkswagen Group), only the diagnostic tool is connected. If nothing particularly unusual is detected, they will first replace the very expensive mass airflow sensor (MAF). If that doesn't fix the problem, they'll shrug their shoulders or dismiss you as crazy. Apparently, there's no one there anymore who really wants to delve into the issue. It's sad and expensive; I spent 324 euros for nothing.

I actually have a perfectly functional LMM (likely referring to a mass airflow sensor) lying around. Should I reinstall the old one and sell the new one?

flightmaster wrote:

I'm experiencing exactly the same symptoms as "mhernach" did.

In addition, there's a surging acceleration behavior around 3000 RPM and under heavy load.

mhernach wrote:

Hi. Are you here, considering all of this?

Smoke, absolutely not.
really sure

A stuck-open EGR valve under high load, for example, can increase soot production, and I think that's probably what happened in your case }.

Otherwise: Glad to hear your car is running properly again.

Even though nothing was smoking in my device, all the symptoms disappeared after I cleaned it.

flightmaster wrote:

Nothing was smoking with me either, and yet, after cleaning, all the symptoms were gone.

Hi.

Surprisingly, this means that at most, only the normal excess air was being lost into the exhaust, so the EGR valve wasn't fully open yet.

Question for everyone:
How can the engine efficiency decrease so drastically that it results in a significant increase in fuel consumption and a loss of power ?

'For years, I've been driving the same route. At some point, the fuel consumption increased from approximately 4.9 to approximately 5.5 liters, not suddenly, but steadily. Additionally, the noticeable drop in power around 3000 RPM became more and more pronounced.'
After I replaced the LMM (mass airflow sensor), diesel filter, and the turbocharger's pressure regulator for a lot of money, but the problems persisted, I cleaned the EGR valve and the intake manifold, and since then, the car has been running fine.

The fuel consumption has decreased to 4.8 liters since the last refueling.

Why would I lie? The driving experience annoyed me for 50,000 km.

flightmaster wrote:

...After I replaced the LMM (lambda sensor), diesel filter, and the pressure regulator for the turbocharger, spending a lot of money, but the problems were still the same, I cleaned the EGR valve including the intake manifold, and since then, the car has been running fine. The fuel consumption has decreased to 4.8 liters since the last refueling. Why would I tell lies? The driving experience annoyed me for 50,000 km.

Hi.

Now it all makes sense.

Your problems likely stemmed less from an obviously malfunctioning EGR valve, but more from the engine's breathing difficulties caused by the clogged intake manifold .

This makes the symptoms understandable... and it seems, in my opinion, that we have the first "documented" case of gradual performance loss due to the exhaust gas recirculation system, which we'll call the "AGR crutch" .

That's actually a valid way to look at it.
I've been keeping a mileage log since I got the car. Around 40,000 kilometers, the fuel consumption started to increase.
The pressure and suffering I was experiencing were likely only now severe enough that I am only now seriously addressing the problem.

I'm not yet able to say what influence the now-defective EGR valve has.
Hopefully, that's the only negative thing, besides the audible noise from the charger.

By the way, I'm having a huge problem with the air conditioning system. Maybe someone here can help me with it from a legal perspective.
I described everything in the bodywork forum.

A huge thank you for the expertise of the forum participants. Without this input, many people would certainly have been lost when discussing things with the 'friendly' person.
Only arguments matter.

Best regards,

Hello,

I'm experiencing similar effects as described by 'flightmaster.' I have weak power in the range of 3000 RPM. I've already tried a lot of things (air flow measurement, voltage testing using the blinking method...). I'm now going to order some seals and will get around to working on it sometime.
'Where exactly is the metal piece stuck? Right above the EGR valve, or further down? It's possible that a similar piece could get stuck in my car too, and then the EGR valve could become defective.'
I can definitely imagine the issue with the lack of airflow. I recently installed a new air filter, and after that, the effect wasn't quite as pronounced.

flightmaster wrote:

"There was so much carbon buildup in the intake manifold (6mm behind the AGR valve, and 2mm directly on the cylinder head all around) that I cleaned it by filling it with gasoline in my father-in-law's fireplace and burning it out. It sputtered and hissed like a burning oil well for over an hour. Afterwards, I could easily knock out the remaining residue." . . .The first test drive made me very happy. The performance is like it used to be, the engine response is much better, and the fuel consumption has decreased by almost 1 liter.

@Rainer:

I believe it would be appropriate to add another point to the "other causes of power loss" section at the end of the VAGCOM troubleshooting guide, ideally right after the one about the EGR valve, something like this:

"Restrictions in the intake path caused by larger oil and soot deposits (layer thicknesses of approximately 5 mm or more) in the intake manifold near the EGR valve and behind it - often recognizable by a too-low actual air mass value at normal boost pressure, where replacing the mass airflow sensor often does not provide a fundamental improvement."

ulf wrote:

... @Rainer: I believe it would be appropriate to add another point to the "other causes of power loss" section at the end of the VAGCOM troubleshooting guide, ideally right after the one about the EGR valve, something like this: "Restrictions in the intake path caused by larger oil and soot deposits (layer thicknesses of approximately 5 mm or more) in the intake manifold near the EGR valve and behind it - often noticeable by a too-low actual air mass value at normal boost pressure, where replacing the mass airflow sensor often does not provide a fundamental improvement"

Hi Ulf,

Just create a few "dummy" entries under the "Articles by Authors" section, and I can then copy and paste my existing articles into those entries (I can edit posts, but not create new ones under your name).

Best regards, Rainer.

Rainer K. wrote:

Just create a few "dummy" entries under the "Articles by Authors" section.

I can then copy and paste the existing articles into those entries (I can edit contributions, but not create new ones under your name).

Hi Rainer,

Okay, I'll do it with "my" articles.

I can copy and paste myself (already }), so you don't need to do that work.