A4 Cabrio 2.5TDI BDG: grauer Rauch bei Kaltstart | Beiträge 48+

That looks good, so it's definitely not the pump setting on the VP44.

Okay, kein Problem! I'm ready when you are. Just paste the text you want me to translate.

What I forgot to write is that the transparent hose to the VEP never had any air bubbles, at least not when I was fiddling with it and looking at it.

My current assessment is that the glow plugs are at least okay, the injection start is correct, the fuses in the MSG housing are intact, and that the dual temperature sensor shows plausible values.

Now I'm wondering: what should I check next?

The service technician at Audi threw a leaking injector into the mix when he saw the video of the cold start.
I can even understand that, as it does indeed look like unburnt diesel.
But: why does it only leak when it's cold? Is that possible?

Where would you look next? Can the 'health' of the injectors be determined using VCDS somehow?
The values for idle stability are falling out of range for cylinder 5, with values up to -1.7. Would that be a possible indication?

[quote]Is it possible to limit the 'health' of the nozzles using VCDS somehow? [/quote]
Okay, here's the translation, keeping the HTML tags, BBCode tags, and URLs intact:

Yes, the idle regulator shows problems with the nozzles as well as differences in the compression of the individual cylinders. 1.7mg/H is still okay, I would consider all values below a magnitude of 2.0mg/H to be perfectly normal.

I fear that further troubleshooting would only make sense if it's cold again. It would be conceivable to have a coolant temperature sensor that only provides incorrect values at cold temperatures, which I have experienced before.

Otherwise, simply continue to observe the situation, now the car is running.

Best regards, Rainer

Hello Rainer,

You were probably right. Thanks for your tips.

The temperatures rose so much during the winter, when I finally got an appointment, that the phenomenon no longer occurred.

And otherwise, the car is running perfectly. So, it seems we just have to wait and see what the winter brings.

Okay, it's finally cold. The outside temperature displayed by the KI was 3.5 degrees, and the coolant temperature was initially 6.6 - I think that's an acceptable difference.

I've also proactively charged the battery to rule out the battery as the cause of poor starting. However, I had been driving for a long time beforehand, and the charger (CTEK) was finished after less than 3 hours, so the battery was actually quite well charged.

This engine start was, interestingly - I think thanks to the long time from ignition to starting - exactly as in the video: a longer (1-2 seconds longer) "whining" sound, with a lot of blue smoke, but not as unevenly running engine.

From this, one could naturally conclude that it was indeed the starting system, but now the engine is running more smoothly than in the video, since all the cylinders were starting poorly, or?

Attached is a log, but it's important to note that there were more than 60 seconds between ignition and engine start, as the HW update to 1.96 had to be installed first.

So, I'll have to try again, but I'm still attaching the log here.

Are the MWB (Motor Warm-Up Box) settings I've chosen appropriate and informative?

And: I need a few seconds to select the MWB settings, during which time the glow plugs are probably already cold. Will I lose the selected MWB settings if I briefly turn the key off and on again, or can I still get realistic values?

Hi,

could you please provide a car scan so that I can learn more about the vehicle? You mentioned that the light bulbs were replaced, but how do you know that the correct ones (length and resistance) were installed?

Best regards, Rainer

Hello Rainer,

attached is the car scan. The last one, which was about five months ago, didn't show any errors.

The problem with the door control unit is new - I had a collision and the rear bumper was replaced. Could it be that something was damaged during that repair?

...and I don't know if the correct candles were installed.
I had them replaced at the local Audi dealer.

Okay, now we can also include attachments...

...and another log when starting up. The first few seconds are missing because the control unit needs a few seconds to come online.

At least, I can see here that cylinder number 1 is noticeable in both logs. Or, cylinder numbers 3-6...

With running rate control values between -2.0 and +2.0 mg/H, it works perfectly.

Best regards, Rainer

Hello Rainer,

Thank you for your assessment.

However, it still makes sense to continue checking the glow plugs, right?
The smoke formation and starting behavior after starting with 1 minute of ignition were very similar to a "normal" faulty start at low temperatures, only worse.

From this, we can conclude that the pre-heating system is actually the problem.

Hi,

[quote]However, it still makes sense to continue checking the light bulbs, right?[/quote]
Since the probability of a mixed installation is quite low, it would be sufficient to remove a light bulb and check its function and correct model.

Best regards, Rainer

I'd also like to share my thoughts.

Since the static adjustment of the VP44 seems to work and the engine speed control
doesn't suggest any mechanical problem - I would actually listen to Rainer's advice and check the type of spark plugs.

In addition, I have a personal experience with this engine: pour a full cup of oil or diesel or whatever is there into the recess with the installed spark plugs.
Start the engine and see if it's bubbling. Then verschandeln it again.

It can be damn difficult to get these sealed properly. If a conscientious Audi mechanic tightens the spark plug with the specified torque, then
it's possible that the spark plug is not properly sealed in the cylinder head.

Best regards,
Sascha

Hello Sascha,

thank you for your response!
I am currently on vacation and therefore not near the car, but I will check the type of candle used (with the help of someone else) as soon as possible.

There is definitely something wrong.