A4 2.0 TDI: Rough Idle Troubleshooting

Hello,

Currently, I'm experiencing an issue with my 2006 Audi A4 where the idle is very rough when the engine is cold.
The speed fluctuates by as much as 90 RPM.

There is also noticeable shaking or jerking when the engine is cold, even while driving at approximately 1500 RPM.

There are no more error entries after the error memory was cleared a few days ago.

The following errors were previously stored.

- 001139 - Exhaust gas pressure sensor 1 (G450): Short circuit to positive.
P0473 - 000 - - - Intermittent.

- 009299 - Diesel particulate filter differential pressure sensor: implausible signal.
P2453 - 000 - - - Intermittent


The idle air control valve for the fourth cylinder requires approximately 1.9 mg/hour of air during cold start-up in idle mode.

The air mass flow rate was approximately 450 mg/H under the existing problem, and approximately 320 mg/H at idle.


Where could the problem be?

Luftmassenmesser? AGR-Ventil? PD cable assembly?

What measurement values should I log?


Thank you very much.

Hello

The second error is a direct consequence of the first error!

I would investigate this primary fault first! In 90% of cases, the sensor itself is defective and has a "short circuit to positive" and needs to be replaced! The remaining 10% are likely due to the wiring harness and hoses (e.g., damage from biting or abrasion).

I'm telling you, it's 90% likely that the sensor itself is the problem! Check the measurement blocks 67/68 to see if the sensor is working – if not, replace it.

Ah yes, the G450 sensor is integrated directly into the housing of the differential pressure sensor.

"How long have you been dealing with this issue? It's possible that the filter has become overloaded as a result of the problem. However, that's less likely."

Here's a picture of our forum administrator, "dieselschrauber," so you can see what I mean.

[img]/download.php?id=4645[/img]

The sensor is working, and the error memory is empty.

Could this error be related to the idling problem?

Possible. Are the sensor readings plausible? What does the filter loading status indicate?

The sensor is working and the error memory is empty.

Can this error be related to the idle problem?

How do you conclude that the sensor is working correctly?
Which pressures are displayed?

The parts tend to break very easily.

Due to the faulty sensor, the filter can become clogged, which can also lead to idling problems.

That's exactly what I meant by "overloading" the filter! That's also why I asked about the plausibility of the values!

I think the price of Asche is around 55.

In which area should the sensor be located?


Thank you.

Doesn't VCDS say that?

I have reviewed the measurement data again.

The differential pressure above the particulate filter is -12.75 and changes when the accelerator is pressed.

What I've noticed is that during the rough idle, the control signal for the EGR valve is around 50% and fluctuates.
The air mass concentration is approximately 280 mg/H and also fluctuates.

The problem disappeared suddenly. Afterwards, the EGR valve control was at 99% idle, and the air mass was 485mg/H.

That suggests a faulty EGR valve.

Thank you.

I would recommend that you proactively clean the AGR valve during every inspection interval.
They tend to accumulate quite strongly in the oil shale.

You can test it using VCDS with the actuator test function.

Is the EGR valve on this car also "normally" vacuum-operated?

The AGR (Abgasrückführung valve) is electronically controlled, and the TE (turbocharger) is likely also electronically controlled.

Here's a picture of my AGR.
However, the function was fully defined.
http://stefan.localh0rst.net/albums/Audi/egr_ventil.sized.jpg