Log Files: Analysis and Troubleshooting

Hello.

Here's a question for the experts. Yesterday, I did a LOG diagnostic test on an Audi 2.5 TDI AKE manufactured in 2002. However, I couldn't find any inconsistencies. Maybe someone else will spot an error?

Please attach the files.

Hello,

And what's the problem?

Best regards, Rainer.

Hello, someone should be able to identify the problem. But if all values are in order, I'm also at a loss. I have a hesitation/jerking in the partial load range, regardless of the engine speed. Camshafts, etc., everything is fine, turbo is okay, pressure sensor is okay, N75 valve is okay, and several other minor things like the MAF sensor has been replaced...

I'm stuck and don't know what to do next. The problem isn't serious, but it's incredibly annoying. I've even considered buying a replacement engine...

First of all, you should have the engine control unit (ECU) reflashed to its original software... have you considered that the car might then run smoothly without any jerking?

Comes with a chip, but has already covered 100,000 km.

The classics would be issues within the powertrain, a faulty VP44 pump, or problems with the injector control valve. The injection timing in the last two logs looks good, but before that, the actual value is zero for quite some time.

"=0 means..."

The jerking only occurs under partial load; when I press the pedal harder, there's nothing noticeable. When driving in traffic and keeping the pedal in a constant position, it jerks a lot. It's most noticeable at around 1400 RPM.

I've also considered that it might be similar to what's found in a 1Z... like the mass airflow sensor (MAF).

Disconnecting the needle valve doesn't improve anything. There's no play in the drivetrain; it's definitely coming from the engine.

What does the idle speed control system indicate (measurement block 13+14)?

The idle speed control is also working correctly, as far as I remember: the range is from -0.21 to +0.67, which should be within acceptable limits. The camshafts are also fine after visual inspection; there are no signs of wear or damage.

Idle speed control: Sum all the values; the result should be approximately zero.

For example, in a 4-cylinder TDI engine:

-0.21
+0.40
-0.25
+0.05
Please provide the text you would like me to translate from German to English. I will then give you only the translation, without any explanations.

-0.01 >>> OK

Similarly, a 5- or 6-cylinder diesel engine could be used, but with only one or two more values.

"The way you're specifying a range of values here, using '... to...', isn't the correct method for diagnosing whether the LLRR is functioning properly."

I'll log the values again and calculate the totals... but I don't know the exact numbers off the top of my head right now.

Here are the values again, for those in the know:

Cylinder 3 = 0.55
Cylinder 1 = 0.00
Cylinder 6 = 0.16
Cylinder 4 = 0.71
Cylinder 5 = 0.24

I couldn't find cylinder number 2.

Rene N. wrote:

Here are the values again, for the experts. Cylinder 3 = 0.55 Cylinder 1 = 0.00 Cylinder 6 = 0.16 Cylinder 4 = 0.71 Cylinder 5 = 0.24

It can't be correct like this because the signs are missing, but the absolute values seem to be good.

Quote:

I haven't found cylinder 2

.
Oh no... please also try reading a bit and using the search function here; I just mentioned a few posts ago that cylinder 2 is the reference.

At least when idling, it's less likely to experience any jolts or jerks.

Generally, you should only post/log values where a problem actually occurs, and not from any operational states where everything is okay.

A classic scenario would be a distorted air mass sensor reading within the ECU, which is now becoming noticeable as jerking or misfires due to increasing wear and tear.
I don't know offhand how the speed signal is implemented in your car, but if it's coming from a sensor on the transmission/differential, please try disconnecting that connector. If the jerking stops then, you've found the problem.

Best regards, Rainer.

Okay, I'll check that out. Otherwise, I haven't found any other errors that would be the cause of the problem. Thanks for the suggestions.

Boost pressure is also okay, measured with an analog gauge. There's a slight overshoot when the boost builds up, around 1.9 bar, otherwise it's about 1.6 bar. The turbo has no play, no stiffness, nothing .

Could it be that a faulty throttle valve in the ESP system is causing the problem? If so, how can I identify this based on the values displayed? My suspicion is actually the ESP system, although when I press the accelerator pedal fully, it seems to work fine.

Okay, don't touch the differential connector. Can anyone tell me which cable or pin on the control unit comes from the speed sensor?