Axial Play VP37 Audi AEL

Hello everyone,

First, let me introduce myself. My name is Mario, I am 37 years old, and I come from Lower Austria.
I've been driving/owning an Audi A6 2.5 TDi Quattro AEL with 340,000 km for 3 months, which I use as my daily driver. (Fuel consumption is 7.7-8.7 liters per 100 km, mostly rural roads and city driving).

Unfortunately, I'm currently experiencing a problem where my engine is running too rough and seems uneven.

When I first got it, it started up wonderfully, but it seemed to lack torque at low RPMs.
I then looked at the dynamic start-up setting, which was at 95, so I changed it to 50. This immediately resulted in a noticeable increase in power from the low RPM range.
Unfortunately, this significantly reduced the engine's revving ability above 3000 RPM, and also negatively impacted its starting performance.

Since it had been over 6 years since the last timing belt change, I decided to replace both belts, including the tensioner pulleys and vibration dampers.
I also adjusted the pump statically to 0.32mm, which resulted in a value of 0.26mm after two calibration runs.

What I noticed about the pump, when I removed the belt, was a relatively large amount of axial play in the pump shaft, but this was no longer noticeable after tightening the new belt!?!

With the dynamic fuel injection start timing, I'm now at 63 degrees at 123 degrees Celsius of fuel temperature. With this setting, it starts up relatively well again and has good power even at low RPM, and it also revs much more smoothly towards 4000 RPM.

Unfortunately, in my opinion, it runs much too roughly at idle, which means you feel a relatively large amount of vibrations both inside and outside the car, which bothers me extremely .

I've only ever driven gasoline cars before, so I'm not used to anything like this at all.

Here's what I'm going to do next:

Refurbishing of fuel injectors by Henzo.
+ Two-mass flywheel with clutch.

Otherwise, I can't really think of anything else that could be causing the rough engine running, except maybe the connecting rod or crankshaft bearings, although I've already driven 3000 km with this problem, and it's not getting worse; in fact, sometimes it even seems better .

What I noticed today is that when comparing the values with 4 cylinders versus 3 cylinders, I suddenly have 95.00 mg/H, and the injection amount during idle sometimes jumps from 5 mg/H to 6 .

I hope I'm not overwhelming you with this, but I'm really annoyed by all of this, and I'm at the end of my rope .

Regards,
Mario.

Hello Mario,

Based on my professional experience with similar pumps, I believe yours should be able to handle that mileage.
Speak plainly and simply.

You can best check the function of the injection timing adjustment by examining the target and actual values of the injection start in the engine control unit's data blocks, specifically at idle and at full load (4000 rpm).
The diesel filter should not be clogged, otherwise the fuel injection timing will no longer function correctly.

It's possible that the achievable operating range has become too small. It's better to adjust the pump so that the car starts well and the target value for the fuel injection start at full throttle is still reached.

You can tell if individual cylinders/injectors are having problems by looking at the readings from the idle speed control system.

Best regards, Rainer.

Hello and thank you for the quick response.

Right now, I kind of think the pump might be the culprit.

Unfortunately, the previous owner could not provide me with more specific information about the repair status of my vehicle, because although he owned it for 3 years, he only used it as a summer car and, of course, never had any problems with it .
Unfortunately, I don't have any information about the owner before the previous owner, but they likely took very good care of the vehicle.

What I noticed during the last test drive was that the injection start point had increased to a maximum of 176, whereas according to the repair manual, it should go up to 210.

Because I haven't actually replaced the fuel filters yet; I really need to do that tomorrow. I've always been too lazy to do it until now .

P.S.: For the moment, I still have to make do with my car, the Dia S101, but my VCDS is already on its way to me .

I would simply take an identical engine for comparison. Compared to a gasoline engine, a TDI engine from the first generation, which is almost 30 years old, is more comparable to a truck in terms of its running smoothness...

Several factors can cause a rough engine running, such as electronically controlled engine mounts, a flexible pipe to the catalytic converter, or the catalytic converter itself.

I used to drive the ACV in my T4, but it runs roughly from the factory.

Hello,

Of course, I've already done that. A friend of mine has an A6 Ael automatic with 210,000 km, and it runs much smoother than mine, despite having a leaky pump .

Well, I quickly replaced my fuel filter earlier, let's see if it made a difference!

I took the trouble to disassemble the old filter, and there was already some dirt present.

Regards,
Mario.

Then check the engine mounts; they can make a big difference if they're broken.

Hi,

So far, I have inspected the visual condition of the hydraulic accumulators. They are definitely sealed, have some minor cracks in the rubber, and the electrical control system is also working perfectly.

Is there any other way to check the inventory?

I have already replaced the gearbox bearings, but unfortunately, there has been no significant improvement.

What I've noticed again today is that the injection amount fluctuates between 5mg and 6mg approximately every 20 seconds, which also causes a slight fluctuation in the engine speed of about 30 revolutions per minute.

Could this be caused by axial play in the pump, or is it more likely due to a contaminated flow control valve?

Hi,

Today, I installed a set of injectors that were previously refurbished. I think the old ones might have been refurbished before too, because they were relatively easy to remove.

In addition, I have also looked into the idle speed and the fuel injection amount at idle.

I've also adjusted the dynamic start setting back a bit; now I'm right at the upper limit (49-51) on the graph. Before, I had it set to 63, so I'm curious to see how it starts up in a cold state now!

With the slight increase in the long-term fuel trim (LLT) to 800 minutes and the reduction in fuel injection quantity (4.7-5), it now runs a little smoother.

Besides, I briefly disconnected the control relay for the engine mounts, but nothing changed, so it seems my mounts are probably at the end of their lifespan.
But that, in turn, would explain the rough idle.

I think the next thing I need to deal with is the pump. The question is, should I look for a used one or try to find a replacement pump? Does anyone know of a reputable company that deals with these things?

Of course, I had to test the K-Power program right away . Unfortunately, I can't seem to upload the diagram here .

Mario-2461 wrote:

Of course, I had to test the K-Power program right away : Unfortunately, I can't seem to upload the diagram here

.
Sure, that's possible, and it's best to do it together with the corresponding log file.
When posting, click on "Select file" or similar.

How about simply presenting some data/log files here?
Let's get started.
- MWB 1 at idle.
- MWB 4 (Einspritzbeginn Soll/Ist)im Leerlauf und beim Beschleunigen im 4. Gang; walk; manner.
- MWB 13 + 14 (Idle speed control).

What is the axial play of the pump shaft? I can see logically that it's less noticeable with a timing belt, because you're moving against the tension of the timing belt (also axially).
hg
Herbert.

Hello,

Sure, I can definitely do that as soon as I'm back at my computer. X

Here's a photo of my performance measurement. I took the weight from the vehicle registration document (1610 kg), but I'm sure my A6 Avant is heavier than the standard specification due to modifications (axles and brakes from an S6, leather sports seats, air conditioning, etc.).

The measured power output is fine, but I can't quite explain the lack of torque and the corresponding torque curve! I measured it in 3rd gear.