Problems with idle speed control and throttle valve!

Since I'm still annoyed by the idling vibration in my car (the engine runs smoothly, but the whole car vibrates), I finally had some time today to read the diagnostic data blocks related to this intermittent issue.

The air conditioning was on during the measurement. Hopefully, that didn't affect the results.

Der Fehler selber tritt erst bei Außentemperaturen über 20°C auf. {M

The following values are then outside the tolerance range:

Measurement block 1.

860 revolutions per minute (RPM) / 8.2 mg per injection / 1.960 volts / 90.0 degrees Celsius.

The voltage of the regulator is too high.

Measurement block 13.

0.32 mg/dose - 2.77 mg/dose - 0.37 mg/dose

Cylinder 2 is running too weak.

Desweiteren sind alle AGR- Werte außerhalb der Toleranz!
My question is: Is the control voltage high due to the large difference in the idle speed regulation? Could there really be problems with compression, or would the deviation be higher then?

I am grateful for any advice.

Regards,

Manuel .[/b]

Hi,

Are your injectors still the original ones? It might be a good idea to do a compression test and see if this anomaly in the fuel injection amounts (idle stabilization) can be traced back to that.

Best regards, Rainer.

No, the nozzles have about 8,000 km on them, and since they were installed, the problem has actually become much more severe! Before that, it only occurred occasionally.

With the nozzles, I also got a new spark plug!

Sure, here is the translation of the text from German to English:

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I'm sorry, but I cannot provide a translation without the text you would like me to translate. Please provide the German text that you want translated into English.

Hopefully, the loose injector that was causing the problem got damaged by all the shaking, and the one they installed now is for cylinder 2.

I'm getting a compression test done on Monday. I hope everything is okay!

I highly doubt that, because the fuel consumption, cold start performance, and power output are all 100%.

And if the problem were due to compression, why does it only occur above 20°C?

Friendly wants to replace the pump and nozzle!

It's terrible when there are no error codes stored in the system's memory.

War sogar in einem BOSCH- Dieselcenter. Dort bekam ich die Antwort: Wenn das mein Diesel wäre, würde ich das so lassen! Stört doch nicht wirklich!

It's incredibly frustrating when the guys don't know what they're doing!

How can I interpret the bias voltage? What does it tell me?

Regards,

Manuel.

Hi,

The control voltage is a measure of the deviation of the setpoint actuator, indicating how much gas the electronic control unit (ECU) is currently supplying.
Just try moving the entire injector assembly, including the component responsible for idle speed control, to a different cylinder and see if the high pressure reading follows it.
Since the value is negative, I suspect the nozzle is leaking (due to overheating or mechanical damage).
In this case, I would simply replace the nozzle (or the entire nozzle assembly, of course).

Regards, Rainer.

EDIT: Are all auxiliary components functioning correctly? Is the belt tensioner for the auxiliary drive okay? Are the pulleys in good condition?

Have you ever considered the possibility that your machine's two flywheel components are defective?
Because an engine at idle shouldn't surge or jerk if the fuel injection timing is correct.

I don't have a dual-mass flywheel on my 1996 AFN, do I? It doesn't jerk; the car vibrates. But only starting at around 20°C.

Heute war ich nochmal da. Außentemperatur 21°C. KTurn off the lime.

Measurement data block 1.

860 revolutions per minute (RPM) / 4.6 mg per injection / 1.640 volts / 88.2 degrees Celsius.

Measurement block 13.

0.68 mg/dose - 1.34 mg/dose - 0.23 mg/dose


This time, all values were within the tolerance range. Notably, the injection amount in measurement block 1 has been halved. The tolerance in the idle speed control is positive for cylinder 2 this time, meaning it's stronger than cylinder 3. Therefore, I am initially ruling out compression problems. On Friday, I have an appointment where the injectors from cylinder 1 will be swapped with those from cylinder 2, as Rainer K suggested!

The start of injection was also dynamically checked, and it's perfectly aligned!

But, typical of my luck, the fuel injection pump is broken.

Keep me updated, and I remain grateful for any help with troubleshooting.

10 minutes after the measurement mentioned above, the jerking started again! It stopped just now after a thunderstorm and with only 18°C outside temperature.

Regards,

Manuel.

Hi, I have a 1999 A4 TDI Avant (AFN engine, 180,000 km) with the same idle vibration problem (even with the air conditioning off)! If you've already found the cause, it would be great if you could let me know (unless it's something expensive like the fuel injection pump - in that case, I'd rather not know!).
So, I hope you can make me smarter - Best regards, Aladdin from Austria.