Saugrohrdruck Regeldifferenz, LMM i.O.?! | Posts 16+

Hmm, so you're saying the LMM is broken?!

He doesn't produce any smoke at all; everything is completely normal, just like you would expect from a diesel engine with 46,000 km .

audi80_cabrio_TDI wrote:

Hmm, so you're saying the mass airflow sensor is broken?!?

I'm leaning more towards the LD sensor or a dirty/porous hose in that area (within the manifold).

Okay, I guess I'll have to take a look at the hoses. However, I'm not entirely sure where the MSG (Mass Air Sensor?) is located on my convertible; it should be on the passenger side under the carpet, right? Maybe you can tell me the best way to access it. Unfortunately, I wasn't there when the engine was chipped; that was done by the previous owner.

Just follow the wiring harness.

And of course, the hose from the intake manifold.

With the VW Golf 3, you'll end up in the engine bay – right in the middle.

Oops, the red color doesn't mean anything; it relates to a different question.



Okay, please provide the German text you would like me to translate into English. I will only provide the translation.

Hello!

I took a look at the hoses for the MSG today.
Okay, I definitely can't find any hoses on the intake manifold.
The wiring harnesses are bundled together and routed directly into the car on the driver's side.

However, I was able to find two thin, black hoses that had been cut right underneath the battery compartment; one leads to the brake booster, and the other goes into the car's interior.

I found the other one again, hidden behind the carpet under the glove compartment. It ends there and connects to a component.
What makes me suspicious is that there's also a large GREEN hose underneath the carpet, leading towards the floor. Doesn't this more likely have something to do with the LD sensor? And why can't I find it in the engine compartment?

audi80_cabrio_TDI wrote:

Today, I took a look at the issue with the hoses connected to the MSG. Okay, I definitely can't find any hoses on the intake manifold.

According to the parts catalog, the TDI convertible only has the 1Z-type lambda sensor in the intake manifold, which does not include pressure measurement.

Therefore, check the entire length of tubing between the intake manifold and the intercooler. Somewhere, a thin hose should branch off. Follow that hose, and it will lead you to the MSG (presumably a component).

Have you ever checked if the wastegate is opening and closing correctly, and what the preload of the linkage for the pressure sensor is?

Based on the symptoms, the cause might be related to this: you likely don't have enough time outside of the normal operating range in the lower gears for the emergency mode to activate.

Low boost pressure occurs when the wastegate is slightly open all the time.

However, I'm not a specialist and haven't analyzed the measurements. I just had the same problem myself and solved it this way.

Tom.

Hello,

Check pressure hoses - Registered air but no boost pressure!
Check if there's any oil leaking on the turbocharger boost hoses or if there's a crack in one of them.

Best regards,

Hi there,

The hose on my Audi 80 B4 with engine code 1Z was also green.
It led from the MSG sensor to the LLK.

See you then.
Markus.

Hello!

Thank you again for all your helpful responses back then!

I found the cause. It was the pressure hose that runs from the coolant reservoir to the sensor in the passenger footwell. It was routed somewhat carelessly under the battery box and had been chafed through by the 'corrugated sheet' located inside the battery box. I cut out about 2cm of the damaged section and then reconnected it using a fuel hose of the correct size and two small clamps.

The problem was initially solved, but at around 180 km/h, it still goes into limp mode. I've logged the entire process. As far as I can see, it's registering too high a boost pressure and a too low mass airflow sensor (MAF) value. (So, the repaired area seems to be airtight...??)
By adjusting the settings, I've managed to reduce the AGR as much as possible. This results in approximately 400-420 mg/L of oxygen in the exhaust during idle. (Measured immediately after coming to a stop).

The wastegate linkage is still moving freely, and the solenoid valve seems to be opening as well.