AFN Brake Pedal Influence on Gas Pedal?

Hello everyone,

I suddenly have a problem with the idle speed of my AFN in my T3.
I noticed this while driving home from work after the van had been in the garage for 2 days.
When the engine stalled at a red light, the idle speed would not drop below approximately 1100 RPM. It wasn't until I released the brake that the engine speed returned to its normal level.
The phenomenon is now constantly reproducible. Every time I apply the brakes, the LL speed does not regulate. This is also not the case even after waiting for several minutes. As soon as I release the brake, it automatically adjusts.

Today, I had a conversation with VAG regarding:
The gas pedal is set to 0.8 instead of 0.0 and sometimes fluctuates between 2.5 and 0.8, even though I am not pressing the pedal.
It seems, therefore, that there is something wrong with the potentiometer... or does it also look like this when the car is cold - i.e., in winter?
The water temperature seems realistic, so I don't think there's a defect.
Error memory is also empty.

I don't really understand what the brake booster has to do with the gas pedal. The vacuum system doesn't really take up that much engine power. Or does it have something to do with the GRA wiring? VAG-com signals match the bit pattern for GRA.
By the way, I implemented my second brake signal using the well-known relay circuit (powered from the brake light circuit). Maybe something went wrong there?

Has anyone got any ideas what might be going on? I will try plugging in my other control unit today to see if the same error occurs here as well.

Thank you.
Greetings
Frebert

Hello again, short update:

Now it seems like the brakes are no longer the issue. I'm currently idling at 1280 RPM and the coolant temperature is 71°C, according to VAG-com. Suctioned air temperature: 19.3 °C (it's cold again in Chiemgau).
The LL speed is now completely off its set point.
Gaspoti shows 0.0 in VAG-com now.

I don't understand anything anymore

It's not the control unit either, because it's the same in the second one.




Greetings
Frebert

Please enter your VCDS license data in your profile, I have a tip for you.

Hello!
What do the brake pedal switches say? Are the switches synchronized?

@ Rainer: I don't have a license, I only have an old VAG demo... Very old... I would still be very happy for a tip!

@ brezelmann01: The two operate absolutely synchronously... and, as I said, it's now also independent of the brake. I can express whatever I want, but the engine RPM is no longer returning to normal!



At 2000 RPM, it smokes grey/blue and smells bad! Hoping it's not just another issue with the turbo or the engine again.
Please carefully monitor the oil level and coolant level.

Hm. Strange. Sounds almost like the emergency function, if the pedal position sensor isn't working properly.

I think smoking is not uncommon at idle speeds. There were also reports about this here in the forum, you should search for them.

Hmm, but shouldn't that then appear in the error memory? But I'll definitely explore and test the Gaspoti further when I have the chance.
Gaspoti also smoothly accelerates from 0.0 to 100 and back down.

Thank you.
Greetings, Frebert

Quote:

Cooling System Temperature 71°C

How to get rid of it?

Background: The combined system (17) uses a different sensor than the engine control unit (01), but both are located in the same temperature sensor.

Hi, Rainer

Quote:

How to read?

VAG-COM 311 in one of the data blocks ... I think 2 or 3 (the coolant temperature is displayed there for me)

Quote:

Background: The combination (17) uses a different sensor than the engine control unit (01), but both are located in the same temperature sensor. icon_idea.gif

Does this mean that there are 2 signals that I only see one of in the measurement block?

Best regards
Frebert

Quote:

Does this mean there are 2 signals that I only see one of in the measurement block?

Sometimes, you'll see one thing in the engine control unit, and something else in the display.
In "normal circumstances", they are both the same. However, it's possible that the combination sensor reads 90°C, while the engine control unit (ECU) reads -15°C.

If the accelerator pedal sensor is detected as faulty by the control unit, a fault entry would be created. Perhaps the donor simply cannot mechanically retract?

Hi, Rainer

I don't have a combination (at least not one that fits AFN - is it the original from the T3)?
The gas pedal operates mechanically without problems, and the potentiometer also functions perfectly (VAG 0.0 to 100), and it also returns to 0.0 every time. I'm going to get a new temperature sensor.

Thank you.
Greetings
Frebert

No problems this morning... not even in the afternoon... strange... hopefully it stays like this.

Hmm, after a good week without any problems, it suddenly reappeared: the increased idle speed. Temperature gauge is okay! Also, the coolant temperature via VAG.
What can I do to find the error?
Thank you, greetings
Frebert

"It's best to check the fuel injection amount at idle (with a warm engine)."

@ Frebert: How did you connect the MSTG's climate input (pin 37)?

@ fantomas: I am currently back to my "normal" idle speed. I drove about 50 km... then on the way home, when I was doing the stop and go from Salzburg, the RPM suddenly dropped back to normal. And it stayed like that for the rest of the journey. Today, after 2 days, the garage is still running normally. I really can't explain this.

As I mentioned, he's back to his normal operating speed. Therefore, I can't measure anything anymore. But maybe next time. What exactly should be checked regarding the fuel injection amount? I think it should be higher than normal, since the RPM is also higher, or what do you think?



@ Wiesel: I don't have a climate! PIN 37 on the MSG is not assigned to me.


I've been driving this bus for 6 years and have never had this problem before! I can't imagine a loose connection. It occurs completely randomly. All temperatures are correct! I've checked the instruments and VAG-COM. I haven't noticed anything unusual. That's not possible!

Can anyone tell me what factors influence the LL (Low Load) engine speed when the engine and fuel pump are functioning correctly?

Thank you, have a wonderful Sunday!
Greetings
Frebert