Schütteln & Beutel A4 1.9 TDI

I'm still stuck on the same problem. When the outside temperature is above 27 degrees Celsius (80.6 Fahrenheit), my 1.9 TDI runs unevenly when I slightly press the accelerator (around 900-950 rpm), and it also stutters as it rolls down and returns to idle, but only at high outside temperatures. The workshop seems unable to really help me; the measured values are okay. At 30 degrees Celsius (86 Fahrenheit), driving becomes an experience. However, this stuttering (like running on three cylinders) always occurs only briefly between 900 and 950 rpm until it runs smoothly at idle again. There's no aftermarket chip installed; everything is completely original. Does anyone have any ideas?

Hello,

What is your engine code?
My washing machine does the same thing, and unfortunately, a solution hasn't been found yet.

Best regards, Rainer.

The fault codes are AFN. It's likely an issue with the electronics, because a temperature difference of only three degrees Celsius wouldn't cause any material changes, and the engine compartment temperature is only minimally or not at all affected by the outside temperature after a longer drive.

Best regards, Lorenz.

Hmm.

Okay, maybe something else then. If you have a climate control system, you can try triggering it by turning it off.
Have you ever checked the vehicle's fault memory?

Best regards, Rainer.

Hello,

The jerking motion during deceleration is caused by some configuration errors in the control program (see error database).
The only way to properly fix this is with a control unit that has the latest software version.

Hi.

Due to my (mostly frustrating) attempts at pump tuning and other modifications, I know that the readings from the HDK sensor change slightly with temperature, even with compensation via a reference coil. This can lead to a slight hesitation (or a somewhat different behavior depending on the temperature) in the initial partial load range (at approximately 1-2 cm of gas pedal at 1100 rpm).
With my fuel pump (AFN), this issue can be completely eliminated by repositioning the upper part of the pump or adjusting the injector control unit, but at the expense of a few horsepower.

@Michael: Regarding the AHF, I recall that "inappropriate" software was identified as a cause of stuttering. Does this also apply to the AFN?

Hello Ulf,

Unfortunately, this also applies to this specific error code.

Hi Michael,

Is there a software update available for the AFN engine? If so, what is the part number of the relevant engine control unit (ECU)?