LMM 3BG / AVF Standgasruckeln | Posts 16+

Hello Rainer,

I measured the blow-by, or crankcase pressure, using the dipstick at idle and at a slightly higher idle speed. It was 230 Pa at idle and then went slightly negative, approximately -300 Pa, with the increased speed. The maximum overpressure that the device recorded was 270 Pa.

I ordered an adapter to measure the cylinder compression, and I should be receiving it this week.

I had some more time this weekend to replace the AGR control valve (pressure transducer) again, but there was no improvement.
AGR sealed - air mass then at idle 440mg/h - all with the old MAF sensor.

Okay, I took the new Pierburg on a longer drive, and I'm still experiencing idle speed fluctuations. Then, during a full-throttle run, the engine check light came on, and the error code "implausible signal from the mass airflow sensor (MAF)" was stored. I reinstalled the old MAF sensor.

Since my intake manifold was quite heavily coated with carbon deposits (about 3mm on each side), I removed it and cleaned it with diesel fuel.

What a mess! After that, I also cleaned the intake ports on the cylinder head, where there was about 1-2 mm of buildup. The intake valve plates themselves were clean.

I also did a log ride yesterday with a weight of 3.8, and I'll upload the data tonight.

Okay, let's talk about the different PDE (presumably referring to pressure drop elements or similar components) that are installed. On cylinder 1, a BC is installed instead of a BA. Can anyone tell me if the BC is compatible?

What other things could I test?

I'm not aware of any different PD elements being installed.

Hello everyone,

Attached again is the error code that was stored, along with the new lambda sensor, which is causing the idle speed to fluctuate up and down.

Here's a log file from last night, after installing a new EGR control valve and cleaning the intake manifold.

Today I noticed a faint chirping sound coming from the front, either on the left or right side, and it reminded me of the power steering fluid (PSF). It might be leaking.

However, if that were the case, wouldn't the air mass in the log be higher, and wouldn't a Low-Level Depression (LLD) be less likely to form?

I ordered another Bosch mass airflow sensor today, let's see what it delivers. The compression tester is scheduled to arrive on Wednesday.

I checked the air mass again today, and with the old mass airflow sensor, it's reading 413 mg/h with the EGR valve closed.

"When I pinch the hose between the EGR valve and the intake manifold to check if too much EGR gas is entering, there's no change! The reading is 417 mg/h."

Rainer, what do you think about the current log?

417mg/H at a closed EGR valve is too low. Either the mass airflow sensor is measuring incorrectly, or you have a mechanical problem.

Oily LLKs (external) always leak... possibly more air escapes through them, and under load, the mass airflow (MAF) values then return to normal ranges.

Best regards, Rainer.

"It's normal for the inside of the liquid cooling system to be oily, and a slight amount of oil around the connector area is also acceptable, but there should be no oil on the outside of the liquid cooling system."

What are the part numbers for the old and new mass airflow sensors (MAF sensors)? There are two different ones for the AVF engine, and they can only be distinguished correctly using the vehicle's VIN.
VG

Hello everyone,

I am aware that there are two different types of mass airflow sensors available for the AVF engine, depending on the year of manufacture or the vehicle's VIN.

The installed fuel injector is a Bosch F00C2G2055. The Pierburg injector that I tested, which had the idle problem and error code, is a Pierburg 7.22684.18.0.

I have now ordered a Bosch part with the number 0281006759.

Chassis number: WVWZZZ3BZ4E120450

Here are some pictures of the mass airflow meter (MAF) and the camshaft, including the pressure drop elements.

I've also ordered a new intercooler from Mahle. When I replaced the turbo and the hoses, the intercooler was completely covered in oil and dirt on the bottom connection, specifically on the side where the plastic connects to the aluminum housing of the intercooler. I initially thought it was coming from the leaky intercooler hose.

Okay, I will swap the mass airflow sensor (MAF) and the knock sensor again this weekend, replacing them with the newly ordered Bosch parts.

I hope my problem isn't caused by the slightly worn camshaft, which might not be lifting the valves enough.

The turbocharger I installed is a Garrett 717858-5010S, which I believe should also be compatible.

Best regards, Sebastian.

Hi everyone,

I hope I'm not bothering you, but unfortunately, things aren't really getting any better.

Yesterday I installed the new Bosch 0281006759 idle speed control valve to eliminate idle problems and error messages, which suggests that the original Pierburg valve was likely faulty.

However, the amount of air in the standing position has not changed, 418mg/h .

Does anyone have any ideas on how I should proceed? I think I'll check the compression next.

Unfortunately, the new LLK (low coolant level) and intake manifold pressure sensor are not yet available.
"I noticed that my ambient pressure reading has been at 960 Pascals for days and hasn't changed. Where is the ambient pressure sensor located in the 3BG model, is it in the intake manifold pressure sensor or in the control unit?"

I am quite desperate.....

Is there anyone from the Schwäbisch Hall or Tauberbischofsheim area here?

Would anyone be interested in joining via Teams and VCDS?

The ambient pressure sensor is located in the control unit. 960 mbar is considered normal, depending on the location.

Since the mass airflow sensor measures the mass of air, the sensor reading should not be affected by the ambient pressure, as the ambient pressure is already taken into account by the mass airflow sensor.

Given your mileage, several factors could be contributing to the low mass airflow (MAF) sensor reading, including excessive blow-by, a potential leak in the intercooler, a dirty intake manifold, insufficient valve lift due to worn camshafts, and unusual intake modifications (such as a mushroom-shaped device that draws hot air from the engine compartment).

If the idle speed is now okay, that's good.

Then, make sure the coolant level is correct and that full power is being achieved, and that's a good thing.

Best regards, Rainer.

Charge air cooler.
"to take a picture" or "to snap a photo"