BDG slightly unstable at partial load, now with power loss

Good evening, everyone.

My uneasy feeling about my recently purchased 'BDG' engine, also known as a 2.5 V6 TDI with 163 hp, is constantly bothering me.

After already experiencing a rough start when cold, and consistently emitting a white/blue cloud into the street (which it still does), the car now has another problem: it was completely empty once before, and today, a new issue arose.

When accelerating with light throttle (maximum 1/8 to 1/4), it intermittently jerks or stutters several times in a row. It's not like the typical misfire, but more like a very brief interruption. The intervals between these interruptions vary, sometimes short and sometimes longer.
Whether the engine is warm or cold makes no difference.
I particularly noticed it when accelerating gently in 3rd gear, between 1500 and 2500 rpm.
The hesitations are quite subtle, but still noticeable... it's like the torque disappears for a quarter of a second.

I hope my description is good enough.

Error memory is empty.
In the idle speed control system, all cylinders are within a range of +/- 1 mg/hour.
Air mass meter is okay (readings are plausible - good Hitachi air mass meter).
I've set the start of injection to 1.4° crank angle before top dead center (BTDC).
'Vintage' is very common.

The only thing that comes to mind is:
I've reconnected the EGR valve. I'll test it again without the EGR to see if it exhibits the same problem. (See my thread about soot in the intake manifold, as a possible cause).
The diesel filter is still old.
I was planning to get a vacuum pump before I replace it.
Condition of pre-feed pump in the tank -> unknown!

Sure, here is the translation of the text from German to English:

'MFG' stands for 'Mit freundlichen Grüßen,' which translates to 'Sincerely' or 'Best regards' in English. It is a common way to end a formal letter or email.

Hello,

As long as the error only occurs sporadically, there is little hope of detecting it, because deviations in measured values will only occur when the error is actively present.

Is the AGR return valve common and clean? Otherwise, a typical issue would be air or foam in the fuel supply due to leaks, or loose connections in the wiring harness/connectors, etc.

Best regards, Rainer.

Hello

Intermittent errors are annoying; I know that all too well.
Diesel is naturally free of bubbles, and otherwise, I don't know what the problem is.

What I can definitely say is:

- My fuel consumption reading on the FIS (driver information system) is off by almost 20%. It's showing a consumption of 8.0 [liters/100km]. In reality, I consumed 6.67 liters per 100 kilometers. After driving 462 kilometers, only 30 liters of diesel fit in the tank. The fuel level was then right up at the top of the filler pipe.

- The cold start today at +5°C was absolutely terrible. On the first attempt, it immediately stalled. On the second attempt, it started up and smoked like a steam locomotive.

- Performance... hard to say. It doesn't feel like 163 horsepower. Something is missing.
I'll test the maximum speed when the track allows it!

Sure, here is the translation of the text from German to English:

'MFG' stands for 'Mit freundlichen Grüßen,' which translates to 'Sincerely' or 'Best regards' in English. It is a common way to end a formal letter or email.

...always pointless maximum speed tests. What's the point? If you're not feeling 100%, you wouldn't run a marathon either.

Just start by checking everything from the beginning. Check the ESP (Electronic Stability Program)... and carefully inspect all the connectors and cables.

Even if the error doesn't occur later, logging can still be useful because someone might be able to contribute valuable insights for troubleshooting based on the collected data.

Good evening.

Okay, so...
Connectors, cables, wires, EGR valve - everything seems to be fine.

- Ladedruck-Ist folgt super dem Ladedruck-Soll. Nur minimale Überschwinger im 1. , 2. , 3. Okay.

- The air mass is also within the target range. At full load (3800 rpm), it peaks at 940 mg/H.

- The fuel injection amount is always at the level of torque limitation.

- The start of injection follows the target value and is set to 14° KW before top dead center (BTDC) and 1.6° KW after top dead center (ATDC) in the default setting.


'The fact that the FIS (Fuel Injection System) deviates from the actual fuel consumption by almost 20% is certainly not without reason; I'm sure you'll agree with me.'
It's certainly not normal for the engine to run as if it's missing 30 horsepower.
In a race against a Passat 3BG 1.9 TDI with 131 hp, I lose starting from 100 km/h.
According to the speedometer, my top speed on a straight road is 205 km/h. It's slightly over 220 km/h going downhill, and 175-180 km/h going uphill.
'In some areas, I'm reaching injection rates of over 40mg/hour at full boost pressure, but you don't notice any difference.'

I suspect that the 20% discrepancy in fuel consumption is likely related to the ESP system and that there's actually a 20% shortfall in the amount of fuel being injected.
That would at least explain the loss of performance.

Best regards and Happy Easter .

Hello,

Perhaps the wrong injectors were installed at some point, or the engine control unit software has been tampered with; in that case, nothing would surprise me.

Please generate a full-load log for measurement block 1 and 11. Does the engine smoke when running at full throttle?
Regarding the starting problems, please check the coolant temperature in measurement block 7 before starting, and then use the TDI timing checker to verify the setting of the injection pump.

Best regards, Rainer.

Hello there!

Since the service history of the car is complete, it was relatively easy for my colleague at Audi to find out about all the visits to the workshop. Apart from a few minor things, not much work was done on the engine.
Nozzles should be original.
When I bought the car, the engine actually started without any problems. Also, on the way home, it reached a speed of approximately 220 km/h relatively well. Furthermore, at the time of purchase, the difference in fuel consumption wasn't that significant. After the first 700 kilometers with the car, the onboard computer (FIS) indicated a consumption of 7.3 liters per 100 kilometers. When calculated at the gas station, it was 7.1 liters per 100 kilometers.
The fuel consumption in the car's computer jumped to 8.0 only last week, and when I filled up the tank two days ago, I calculated a value of 6.6. I didn't make any mistakes while filling up. I pumped gas twice at the same pump until it reached the top of the filler pipe.
To match that, the car can't even reach 220 km/h on a straight road; it tops out at 205 km/h, and that's its limit.
Since the measurements themselves are good, it's likely that the displayed amount differs from the actual amount.
Er ist übrigens absolut ruß frei. Wenn ich im ersten Gang ab 5km/h voll rein trete kommt auch nicht so der Schub. RIt's not happening anyway.

Okay, I understand. Just provide the text you want me to translate from German to English. I will only give you the translation.
The coolant temperature sensor deviates by approximately 2-3 degrees from the outside temperature after being exposed to the elements for about 15-20 hours.
With a warm engine, the water temperature varies between 88 and 93°C depending on the accelerator pedal position.

I'll take some photos later when the road is clear.

Good evening everyone,

My BDG is becoming increasingly perplexing.
I just quickly went out to do some shopping.
I had to briefly slow down to navigate a curve and then drive up a steep hill.

Okay, so it's 3rd gear, 1700 RPM, full throttle. I can hear the turbocharger spooling up, and the engine is accelerating... not great.
Suddenly, at approximately 2400 RPM, the knocking sound becomes louder, and simultaneously, a significant increase in power kicks in abruptly, as if a switch has been flipped!
He did the same thing again on the way home, during a longer straight section of the road.
What is this supposed to be?

Tomorrow, I'm going to start with some logging runs.
Which types of market width indicators (MWBs) should I track to get the most useful information?

Does it start well in the morning after a brief warm-up, but then doesn't run as smoothly after standing for a few hours?

"My engine also has that 'power dip' around 2000 RPM, especially after a cold start. From that point on, the engine sounds completely different (like 'frrrrr') and feels sluggish. Could it be related to the glow plug system shutting off at that RPM?"
"At temperatures where it no longer needs to be pre-warmed in the morning, it still produces a blue-white cloud of smoke, and I have to rev the engine for a relatively long time."
During the compression test, it was determined that cylinders 4, 5, and 6 on the left bank showed poor readings. I don't know why this is happening... The vehicle has a complete service history and has been driven 155,000 kilometers.

Good evening 'exciter'.
'Initially, the engine had a rough start when cold, but it was okay once warm. I then readjusted the fuel injection timing. Now it starts without misfiring, but the white-blue smoke is still present. Creating a cloud of smoke is his specialty.'

I can't say for sure whether the performance issue is also present when the engine is cold. When the engine is cold, I'm very careful with my foot on the pedal. I don't want to hurt it (the car).
It couldn't have been due to afterglow. He had water at 90°C and oil at 100°C.
I can't say anything about the compression on mine; the spark plugs just won't come out.

Sure, here is the translation of the text from German to English:

'MFG' stands for 'Mit freundlichen Grüßen,' which translates to 'Sincerely' or 'Best regards' in English. It is a common way to end a formal letter or email.

Good day.

I finally managed to create some logs today.
I shifted into the first log between 1000 and 4000 RPM in 4th gear, but I could only shift into the second log in 3rd gear. It simply wasn't possible to do it in a higher gear due to traffic.
The file 'logmich' contains some acceleration data in the 2nd and 3rd gears. Perhaps something can be identified there regarding the 'jerk' or sudden change in speed at approximately 2200 RPM.

Thank you for your help.

Good evening.

I just wanted to ask if you've noticed anything unusual in the logs.
Today I drove the A38 almost at full throttle, but it couldn't reach more than 205 km/h on the speedometer. That's definitely too slow, especially with the standard tires.


Sure, here is the translation of the text from German to English:

'MFG' stands for 'Mit freundlichen Grüßen,' which translates to 'Sincerely' or 'Best regards' in English. It is a common way to end a formal letter or email.