Audi 100 2.5 TDI: Lack of Power (AAT)

Hi!

Ich hätte ein kleines, aber um so nervliches Problem mit meinem 2.5 tdi. Es handelt sich darum, dass das Auto im normalen Drehmomentbereich zw. 2000-3000 U/min nach einer Weile an Kraft verliert-so, als es überhaupt kein Ladedruck wäre. LMM, Saugrohrdrucksensor, Magnetventil für Ladedruckregelung (an der Spritzwand)... hab' ich schon ausgetauscht, aber es bringt ja nichts (((( Mein AGR-Ventil hab' ich schon längst eingetippt (mit einer Alu-Platte). Die einzige Lösung ist, dass wenn das Auto das Problem erzeigt (Kraftmangel) trete ich solange auf den Kupplungpedal bis der Motor zum Leerlauf zurückgeht, dann Kupplung hoch und das Auto läuft wieder so wie es sein muss. Was dabei noch merkwürdig ist, dass ich in der zwischenzeit ein anderes Computer drin hatte, mit dem ich das Problem nicht spüren konnte. Dann habe ich mehrere ECU-s ausprobiert, mit manchen hatte ich das Problem, mit manchen überhaupt nicht. Ich hab's gelesen -und gecheckt- dass es im ECU ein elektronischer Druckregler zu finden ist (Das Teil hat eine schwarze Kunststoffgehäuse und wird bei Bosch hergestellt). Könnte sein, dass diese kaputt gegangen ist? Wenn das Problem zu spüren ist, geht der Ladedruck nicht über 0,5 Bar. SoWell, I know that this problem is common in the 100-series TDI models. I also have two acquaintances, besides myself, who are experiencing the same issue.


If anyone could help me, I would be very grateful!

Sincerely,
Anton

P.S.: How can the bypass valve on the turbocharger be checked?

cashmoney wrote:

P.S.: How can the bypass valve on the turbo be checked?

Hi,
I thought you had already figured that out?
Regardless of the cause, the pressure is already low in emergency mode because only a small amount of diesel is injected, which keeps the exhaust gas temperature low.
The control unit might contain an ambient pressure sensor, but if it's displaying Nepal, something is definitely wrong...

Hi cashmoney, I just read that you disabled your AGR valve. I also drive an AEL and I'm wondering if you notice any changes from doing that?
Sure, here's the translation:

"I would appreciate a response."
Unfortunately, I can't help you with that problem. Good luck! Best regards, bastianna.

@bastianna

The improvement from disabling the AGR (Abgasrückführung) is indeed noticeable. A few days ago, I completely restored my AEL (engine) and, at the same time, cleaned the intake manifold... it's monstrous what accumulates there. Nevertheless, I've recently felt that the engine speed range of 1000-1500 RPM isn't being used effectively; the engine vibrates slightly and doesn't pull well. - Explanation: Currently, I drive the Munich bypass highway to work every day. I use cruise control at 95 km/h and comfortably cruise at just 3.6 liters per 100 km. In 6th gear, the engine runs at just under 1700 RPM. However, on a longer construction site in northern Munich, I can only go 80 km/h, and even then, I need to maintain 1400-1500 RPM smoothly.

Until two days ago, things weren't going so well, so I simply switched to setting number 5. Now, with the AGR system deactivated, you can even accelerate quickly from the lowest RPM (800 rpm) (of course, you should only do this experimentally), and my fuel consumption has even decreased by 0.2 liters in my test drives.

I find the AEL so incredibly awesome. It has a lot of power, but also the option of a three-liter engine.

Disabling the AGR (Abgasrückführung) system when using an AEL (Abgasendrohr-Leerlauf) is actually quite simple: remove the T-connector from the vacuum reservoir, connect the hose directly to the pressure reservoir, and leave the AGR valve disconnected. That's it – the setup is complete, and it's also easy to reconnect everything if you want to re-enable the AGR system.

Tuppie.

@tuppi

'However, deactivating the AGR is more cost-effective to achieve with a piece of metal. If the thing doesn't seal 100%, then boost pressure will whistle out through the exhaust, and a loss of power could be the result. Your method also works, but you have to be very sure that the AGR } is sealing properly. I only trust metal pieces that might accidentally fall into place...' }

P.S.: How can the bypass valve on the turbo be checked?
Hi,
I thought you had already figured that out?
Regardless of the cause, the pressure is already low in emergency mode because only a small amount of diesel is injected, which keeps the exhaust gas temperature low.
In the control unit, there might be an ambient pressure sensor, but if it's showing Nepal...

Hi Christian!

I removed the entire exhaust system, but I'm not sure how to identify any damage to the bypass valve. Do you think that when my car exhibits performance problems, the engine control unit activates a limp-home mode? Does it also reduce the fuel injection amount in that case? Sorry for being a novice, but I don't understand your suggestion. How am I supposed to know if the ambient pressure sensor is actually faulty?

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

'MFG: Anton' translates to 'Best regards: Anton' or 'Sincerely: Anton'.

Hi,
You need to apply pressure there using a hose and air pump, a large syringe, or something similar. If no pressure builds up, the membrane is defective. It's difficult to visually determine whether the membrane and the actuation rod are moving, especially with the AAT installed. However, perhaps if the exhaust is removed, although I don't have a clear picture of that in my mind right now.

How did you measure the boost pressure?

Hi,
You need to apply pressure there using a hose and air pump, a large syringe, or something similar. If no pressure builds up, the membrane is defective. It's difficult to visually determine whether the membrane and the actuation rod are moving, especially with the AAT installed. However, perhaps if the exhaust is removed, although I don't have a clear picture of that in my mind right now.

How did you measure the boost pressure?

Hi!

I just had it measured, but I think it was measured on the suction side of the turbocharger.

cashmoney wrote:

I just had it measured, but I think it was measured on the suction side of the turbocharger.[/quote]
That doesn't get you very far. It's not just the altitude at any given moment that's important, but the way the pressure changes during acceleration from below. There's a huge difference whether the pressure remains low all the time, or whether it only decreases after a strong overshoot, triggered by the EDC in an emergency mode.

Hi Tuppi, I disconnected my EGR valve today and I'm curious to see what changes it makes. I also experience that vibration from 1000 to 1600 RPM. After that, it runs smoothly again, and the performance seems okay. Your fuel consumption is amazing; mine averages 6.8 liters. I'm currently researching the topic of using vegetable oil. I've read a lot of interesting and positive things in various forums.

I would like to pose this question to everyone.

What do you think about vegetable oil production?
Looking forward to your contributions!
Hi Bastianna,

@bastianna

The discussion about 'pöl' should not be held in this thread. This thread is about other things. It would be too off-topic.