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V6 TDI white smoke when only warm and on idle

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#22 ·
jeffnhiscars said:
I won't ask how you figured that out :)
Click to expand...
Rats. Tried inserting a gif and didn't work. My point is that something is absolutely up, so we're missing something... A fluid is low somewhere
 
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Discussion starter · #24 ·
I am still busy with the smoke issue. Meanwhile, the following things have changed as well:

  • New DPF
  • New DPF pressure sensor
  • New DPF temperature sensor
  • New O2 sensor

After replacing DPF, I realized that it is not possible to reset the ash value of DPF and DPF pressure sensor (channels 81 and 83) in the engine controller.

Then searching the internet in many Audi forums, I learned that this was an issue back in 2006 and 2007 for V6 TDI cars, and for this, there was a recall for that (TPI 2012786/8). What is my view is happening, since the controller assumes that the ash value of the DPF is too high, it is trying to regenerate endlessly.

So I took the car to VW and ask if the engine controller needs an update. They confirmed it and took the car for the update (Update 23BJ Critical). After three days, they called me that they can not update the engine software because possibly the mass air-flow sensor is faulty. Therefore, I took the car and had:

- New mass airflow sensor.

The car still smokes on idle. I contacted the VW and they speculated that it should be injectors causing the smoke (I dought it because the smoke started with old injectors, and then I replaced all injectors). Anyways, I bought an injector return line test kit and tested the injectors. I have to visit VW next and discuss the test results as well as the software update.

The other thing that I noticed is that the oil level goes high in the long run. This should have either of two reasons:
1. Frequent DPF regeneration
2. Dripping injectors
 
Discussion starter · #25 ·
Problem solved!

I discussed the result of the injector return line test with the VW master mechanic (the return amount on 2 cylinders was less than the average of 4 others).

He speculated that the injectors should be the culprit. Therefore, I removed all 6 refurbished injectors and send them back, and got 6 fresh injectors in return (which had 1-year guarantee). Installing the new ones solved the smoke problem.

The problem was not detectable by VCDS as the timing and the amount of injection looked to be fully in the ideal range. The problem was that the injectors were dripping extra fuel into the cylinders continuously (and hence less returning fuel) and it could only be detected only by measuring and comparing the amount of return fuel (thanks to the 25 bucks test kit from eBay).

On idle, due to a lower revolution, the exessive fuel evaporated and emitted as smoke but in higher revolutions, it could be burned within the normal engine cycle, as it had less time for dripping and evaporation per cycle, and hence no smoke.

So here is a checklist for the smoke problem, in case I would have to do it again:

  1. Check the oil level and the coolant level in the long run
  2. Check the injectors, EGR, and DPF values in VCDS if they are fine and in range
  3. Check if your car needs a software update
  4. Check if there is an air leak in the intake system
  5. Replace fuel filter and air intake filter
  6. Check if the right oil type is used in the engine
  7. Check if the crankcase ventilation system is fine (PCV is fine)
  8. Check if the turbocharger oil line is dripping oil in the intake
  9. Check injectors' return line quantity
  10. Clean air intake system throughly (no carbon deposit)
  11. Check the EGR system if it functions properly (no coolant leakage and no blocked smoke pipe)
  12. Check mass air flow sensor
  13. Check O2 sensor on catalisator
  14. Check the DPF temperature and difference sensor
  15. Check the fuel pressure sensor
  16. Check turbocharger functionality
  17. Clean/Replace DPF
  18. Check the injector functionality
 
#28 ·
When you have eliminated all which is impossible, then whatever remains, however improbable, must be the truth.
Click to expand...
Arthur Conan Doyle, The Case-Book of Sherlock Holmes
Came late to this thread, but appreciate the process of evaluating the problem and the collaboration of getting to the answer. Marvelous!
 
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