Audi Avant 2.5 TDI: Power Loss Troubleshooting

Hello,

I drive an Audi 100 Avant TDI, manufactured in December 1993, with approximately 200,000 kilometers on the odometer.
I have to drive on the highway every day, and usually the car can reach speeds of up to about 215 km/h (according to the speedometer).

Last year, I had a major inspection done at ATU.
ATU essentially carried out the following tasks at that time:

Timing belt for camshaft and fuel injection pump, including tensioner.
Deflector rollers replaced.
2. Fuel filter replaced.
3. Replacement of ancillary items such as air filter, oil filter, valve cover gasket, etc.

After that, everything worked normally again.

Approximately 4 weeks later, the performance loss was first observed.

I first noticed it after I had just performed a quick 'visual inspection of the engine compartment' and realized that ATU had apparently...
I had forgotten to plug in two small black tubes that led into a kind of vacuum chamber. So, I plugged those tubes back in, got on the highway, and noticed a significant loss of power. The car was severely limited, even at a speed of about 190 km/h, and even on a downhill slope, it wouldn't go above 195 km/h.
I then unplugged the tubes again, but that didn't change anything.
brought.
(Later, when I addressed Audi about this and wanted to know if there was a...)
Audi suggested that there might be a connection between the loss of power and the tubes, along with the vacuum sensor, but they thought it was just some kind of switch (?) whose exact function I've now forgotten.

I wanted to test for a while longer to see if the loss of power persists and whether it also becomes noticeable during acceleration.

I will be a bit late, mainly due to problems at the...
Rear brake issue. I drove to a different ATU branch and pointed out the loss of power to the master mechanic. I also asked if this loss of power could be related to a timing belt replacement that had recently been performed.
The ATU technician checked the start of the boost function and said that...
The start date for the funding was not precisely determined by the colleagues at ATU, which was likely also due to the fact that ATU was still lacking certain equipment, making it difficult to be precise.
Unfortunately, the adjusted setting didn't make any difference!

So, shortly after that, I had Audi check again for the cause of the power loss.
Audi then dynamically adjusted the start of the funding period, and...
statically tested and adjusted. Audi said at the time that the old...
Absolutely not (this was already the ATU correction!).
was correct.

Unfortunately, even with the corrected setting, it doesn't make a difference in this case.
brought.

The error memory reported:

1 error detected.
00550 017
Injection start control.
Rule difference.
intermittent error
sporadic error
occasional error

One of these blocks, for example, is:

130 139 255 128 228 239 061 194 196 231
152 117 000 000 178 239 061 197 195 163
211 134 255 077 206 239 061 200 190 187
213 125 255 063 202 239 061 199 192 182
190 120 255 116 225 239 061 199 196 209
170 127 255 119 224 239 060 199 197 219

In these measurement readings, Audi highlighted the second column and placed it next to...
written:
Min. 190 ... 210 (fuel injection start, full load).

Audi then explained to me that the fuel injection pump was no longer working correctly.
'common' and I should try to add 1 liter of engine oil per tankful.
Adding fuel to the tank won't help (it's useless!). Otherwise, the only solutions are a new (and very expensive) fuel injection pump or having the pump refurbished by a Bosch service center.

Yesterday, I was reading in this forum, in a post from...
25.04.2002 'Report - Power loss above 3000 RPM in a TDI engine,' stating that in that case, the power loss was caused by a diesel filter installed by ATU.
It was a VW Golf, model year 1993, manufactured in 1994.
My Audi 100 TDI is also from the year 1993, model 1994. => What's the connection?

I remember that the Audi technician (after I had explained my problems) also asked when the diesel filter was last changed. I told him at the time that it couldn't be the filter, as it had just been replaced (by ATU).

Meanwhile, I'm wondering if the cause of the performance loss is really solely due to the fuel injection pump, or if ATU may have made mistakes during the installation of the timing belt, or installed a faulty diesel filter, etc.

Or are there other, completely different causes to consider?

What do you think, would it make sense to go back to Audi and have them check the work that ATU performed, specifically verifying the correct installation of the timing belt and diesel filter?

I'm asking because I've already had Audi investigate the cause of the power loss.
And in that process, Audi, having quickly recognized that the start of injection was not correctly configured, only encountered issues with certain measurement blocks related to the fuel injection pump.
Besides costing me money, it unfortunately didn't really achieve anything.
brought.

Can almost everything that ATU could theoretically have done wrong be relatively easily detected through measurements or similar methods?
'Or are there some causes that cannot be determined solely through measurement, and must be investigated 'mechanically'?'

I created a folder named 'http://briefcase.yahoo.com/dbmoeller' and placed 2 images inside, which show the 'tube problem' mentioned above. This might be easier to understand than if I tried to explain it. By clicking on the image, you can choose between 'Full Size' and 'Normal Size'. In image 542, you can see the normal condition, and in image 544, I have disconnected the connector with the tubes. Perhaps someone can briefly explain what this vacuum system is for and whether it could be related to the loss of power?

BTW: At first, I thought I could get used to this speed limiter, but when it starts kicking in around 185 km/h, it's quite annoying.

It would be great if someone had a tip for me!
Thank you for your efforts!

Best regards,
Dietmar.

Hello,

The two vacuum hoses connect to a solenoid valve that controls the exhaust gas recirculation (EGR) system. If these hoses are disconnected, the EGR system will not function. A noticeable loss of power is not expected when the EGR system is deactivated.

The error can have various causes:

- Fuel supply not working correctly (e.g., diesel filter).
- Faulty needle valve (integrated into a nozzle).
- Start of funding not in order (suspend).

Based on the experiences shared in this forum, I would initially install an original VAG diesel filter.

Hello,

Meanwhile, I had an original Audi diesel filter installed.
When Audi informed me that I needed a relatively rare filter due to the engine code, I thought (and probably Audi did too) that this filter might actually be responsible for the loss of power.

But unfortunately, that is not the case!

Last Thursday (which was a holiday), I took the car out again for an extended test drive on the relatively empty highway to see how the new diesel filter was performing.
At approximately 175 km/h, a (relatively mild) reduction in power becomes noticeable. The car then struggles to reach about 190 km/h, and that's roughly the limit on a straight road.
Even on a steep uphill section, the car did not exceed 205 km/h.

Now, the following questions arise for me again:

Please provide the text you would like me to translate from German to English.
Is it worth having the work done by ATU (timing belt and injection pump replacement) checked by someone else?
Could errors have occurred during these procedures that could lead to the symptoms described?

2.
The fuel injection system was already deactivated by Audi, and the error memory was read. I have provided the values in the first post.
Do the values or the error message indicate that the fuel injection pump is the cause, or do they rather point to the EFFECT of another underlying cause?


In summary:
How should I proceed? Should I have the fuel injection pump rebuilt without a specific diagnosis, have the work done by ATU checked by Audi, or have Audi specifically investigate and rule out other potential sources of the problem (e.g., mass airflow sensor, injector control valve, etc.)?

What makes sense, especially from a financial perspective, and what would not be sensible?

Best regards,
Dietmar.

Hello,

First, let's talk about the values:

The first column indicates the current speed. This value should be between 140 and 180.
At the same time, the third column must display a value of 255 (indicating the accelerator pedal is fully depressed).
Only under these two conditions can comparable values be generated.
This is only present in the last line of your report (an indication that the workshop only performed a very superficial measurement).

The value in the 3rd column indicates the start of the pumping process and should be between 140 and 180.
The fourth column indicates the injection volume and should be between 115 and 138.
The last column shows the amount of air being drawn in, and it should be above 185.

This leads to the following conclusion:
The LMM (Mass Air Flow sensor) is okay according to these values. However, you can check if there is any oil film on the LMM sensor (see also the error database).
The start of injection is not correct.
The injection quantity is at the lower limit. Considering the value of 170 (upper limit) in the first column, this seems too low.

Question: Was the measurement taken before or after the adjustment?
If this measurement was performed before the adjustment, it is highly recommended to repeat it. This time, also print out the data for display block 4 (fuel injection pump).
If the measurement was performed after the adjustment, then the workshop likely cut corners.

Hello Michael II,

Thank you for your explanation!

Based on my current understanding, I assume that the measurement data listed were obtained *after* the start of the pumping process.
Because after that, Audi had highlighted the second column and written something next to it:
'Minimum 190...210 degrees of crankshaft rotation before top dead center (BTDC) for fuel injection start at full load.'
and told me that the fuel injection pump is no longer 'working properly' and that I should try adding 1 liter of engine oil to the tank (which sometimes helps), or have the pump overhauled or replaced.

Do you think that Audi may have incorrectly configured the start time for the subsidy program, and that a re-configuration (to the correct setting) could resolve the issue?

Could it be that, for some reason, a previously set alignment can become misaligned again (e.g., if the timing belt is not properly tensioned, or something similar), or is that more unlikely?

Best regards,
Dietmar.

Hello,

Based on the data, the pump appears to be misadjusted.
In normal operation, this can also happen through:
- Loose screw on the camshaft sprocket.
- Excessive tension on the timing belt.
- Incorrect/faulty timing belt tension.

I would definitely have the alignment checked again at a different workshop.
Make sure you receive the measurement report afterwards.

Ich würde vermuten Du bist längere Zeit RME od PME /Biodiesel gefahren und die Hubscheibe Deiner Einspritzpumpe hat gefressen und Späne in den Mengen- und Spritzversteller transportiert. Vermutung! Das bedeutet auf lange Sicht Liegenbleiber u. ReRepair of the VP37.

Size M.

Hi.

Quote:

I would guess that you have been running on RME or PME/biodiesel for a while, and the rotor of your injection pump has worn out, causing debris to be transported into the quantity and injection control valve.

Hmm, I always thought that biodiesel and similar products only (sometimes) damage the seals.
But there are concerns about fuel consumption - I've read several times that the lubricating properties are even better than those of regular diesel.
How can "fresser" (presumably referring to something that consumes or benefits) be favored simultaneously?