TDI Idle Problem: 2.5 V6 AKN Engine Issues

Hello,

After using the search function and finding numerous posts about fluctuating idle speeds, but still not being able to identify the cause of my problem, I decided to start a new thread.

A4, December 1999, 2.5 TDI engine (AKN), 77,000 kilometers.

'It starts perfectly and all the characteristics that can be subjectively observed are as they should be. However, it has been noted that after a COLD START, the increased IDLE SPEED cannot be maintained, and there are FLUCTUATIONS around 1000 RPM. This lasts for about 30 seconds, and once the speed is reduced to 900 RPM, the RPM FLUCTUATIONS become smaller and eventually disappear. If I manually increase the throttle, there are no fluctuations at all. Strangely enough, when it's cold enough outside that the engine initially runs at around 1100 RPM, there are no RPM fluctuations – they only reappear when the speed drops into the 1000 RPM range.'

If the outside temperature is above 8 degrees Celsius, it only revs up to about 900 RPM when cold, and you can't notice anything unusual. As I said, otherwise everything is really fine, and a timing belt replacement hasn't been performed.

Has anyone experienced this phenomenon before? Or does anyone know a solution for troubleshooting it? Can I rule anything out myself (initially, without using VAG diagnostics)?

Thank you very much in advance.


Best regards, Joerg B.

Could there be signs of impending pump problems with the VP44? My car started exhibiting similar symptoms (see thread), and my colleague's 1998 AFB V6 experienced the same issue.
My fuel pump failed after 167,000 kilometers and had to be replaced.
It's better to check the pump regularly and avoid letting the tank run completely empty, as water and dirt mean death for these pumps.

@Beeralpina:

Is there anything new?
I have the same problem, mileage is 142,000 km, I've never run the tank completely empty and I've never refueled without diesel, except maybe at the workshop .

My Audi (4-cylinder engine) makes noises like that when one or more glow plugs are faulty.