A4 Cabrio 2.5TDI BDG: grauer Rauch bei Kaltstart | Posts 32+

Okay, sure.
But you recommend expanding them in order to form a well-informed opinion? If they are technically sound, there isn't much else to consider, is there?

No, I already wrote above that they cannot be expanded initially, but need to be measured directly.

Hello Rainer, thank you for the quick responses.
I somehow missed your sentence from a previous post regarding the candle replacement and who should pay for it – with that, you quite clearly stated what "phase" might be.

I apologize for overlooking that; it could have saved some people from posting.

Then I should probably get myself one of those clamp meters...

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I suppose I should probably get myself one of those clamp meters...

Especially since it's available for well under 100 EUR...

I have this product and I am very satisfied: "AC Current Clamp Meter 100 AAC 100 ADC TRMS, UT210E".

http://www.distrelec.ch/de/stromzange-100-aac-100-adc-trms-ut210e/p/30059441?gclid=CPbCr62Xh80CFc1uGwodRDAKUA

You can also find it on AliExpress, and it's much cheaper there.

Best regards, gnasch.

Hi, have you also checked the fuel injection start? If it's set towards "late," it can cause cold start problems and smoking. Also, check for air in the fuel system!

Good point.

PPS: You can check the start of injection using VCDS by going to the corresponding measurement block in the engine control unit, then to the basic settings, and then clicking the button for the TDI timing checker.

Thank you for the tips! I had already found the instructions on how to adjust the injection start.

I also created a log recording idle conditions and fuel injection timing (actual vs. target) over a few minutes of driving.
I tried to measure the current flowing through the wires to the glow plugs. That wasn't easy, as I couldn't really get a good connection to the wires that were attached.
The wiring to the three sensors on the passenger side had a total current of approximately 40A, including the insulation. The wiring to all six sensors (i.e., just before the point where it splits into the left and right branches) had a current of approximately 80A.
The wires I was able to access somewhat easily had individual values between 10A and 15A, but I couldn't really get them positioned nicely within the clamp so that they were centered.

Does this help at all, or should you definitely remove all the brackets and check each cable individually?

Would you like me to delve deeper into the injection start? Should I have used different measurement techniques to get a clearer picture?

Unfortunately, I have another question about KDataScope: When I have logged multiple measurement data points (MWBs), how do I configure it so that I only see specific ones displayed? In this case, it would be interesting to have a graph showing only the target and actual values of the injection start.

Hello Florian,

All measurement data blocks that are present in the log are always displayed. During use of the program, there was never a need to hide individual data blocks.
Generally, you don't log information that you don't need.
And if it's displayed, at least my brain doesn't have a problem ignoring, for example, the yellow line when I'm only interested in the red and green ones.

Regarding the injection start control mentioned by @T3Surfer, it makes no sense to log anything, because it's not about the dynamic adjustment during driving, but rather the static setting that is crucial at the start. Therefore, your log is nice, but rather useless.

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I had already found the instructions for the initial injection rate control.

Please also read and understand the section on the TDI timing checker in the manual.

What would be helpful is a Screenshot from the TDI timing checker. Please make sure the cloud view is enabled and that the environmental conditions (engine temperature) are met. The image you posted previously didn't provide any useful information, so I deleted it.

The "Print Screen" key, under Windows, places a Screenshot into the clipboard, where it can be pasted, for example, into MS Paint. Then you don't need a camera/phone.

With a clamp meter, it's less important where the wire is positioned within the clamp; what's more important is that the clamp is fully closed. Also, from your description, it's not entirely clear where the measurements were taken.
Logically, all spark plugs draw the same amount of current, unless they are defective or the timing (i.e., the temperature of each spark plug) is different.

Best regards, Rainer.

The fuel injection start timing system (Wolke) was activated, the engine temperature was at operating temperature, and at the start of the measurement, the oil temperature was 91°. I was unaware that the fuel injection start timing system has no relevance during driving.
In the cloud view, all the points were located between the blue center line and the green upper line, ranging from approximately midway between the two lines to about 85% towards the green line.
Instead of a cloud, there was a vertical accumulation of points.
It was clear that the cloud was not located on the blue line, but rather roughly in the middle between the blue and green lines.

However, the number of data points gradually decreased during the measurement, so I took the picture before there was absolutely nothing left.

The current measurement: of course, the clamp was always closed.
Here are the measured values again:
Complete string, passenger side bank: 40A.
Wire gauge for both benches: approximately 80A.
Unfortunately, I was only able to access four connection cables individually, and each one had a current rating of between 10 and 15 amps.

"Edit: Added further log, corrected typos."

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I didn't know that the injection start setting has no effect while the vehicle is in motion.

Yes, she does, but she doesn't have it for the static baseline setting.

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I was able to access only four connection cables individually: each with a current of between 10 and 15 amperes.

Then they should be fine.

Best regards, Rainer.

Okay, I have to ask a silly question again:
I'm going to the engine control unit (ECU).
From there, go to the basic settings. If you select "MWB 0" there, you will get a series of zeros and ones.
I have a dropdown menu where I can select "Injection Start." I have selected that option. In the bottom right corner, there's a button labeled "TDI Graph," which I click.
Then, MWB 4 will automatically appear at the top.
In the graph that then appears in a new window, I select my motor.
Now the valve is being adjusted, and you can hear the engine as the values change. A few yellow dots appear in the graph.

Is that correct so far?


Edit: Step added.

Hi Florian, that is absolutely correct!

Hello Rainer, thank you!
Then, in principle, we could re-insert the photo. The graph in the TDI timing checker looks exactly the same as in the picture, down to the minute.
I filmed the whole thing to make it clearer.

I just had a silly thought: is the 'zoom' of the graph simply incorrect? Can it be adjusted?