Further to TDi misfire

[piotrek]

Hi All

Further to my recent question on TDi misfire, the dealer says that its the diesel partical filter working that is causing the hesitation/misfire.
Can anyone explain this one to me?????? :confused:

[toff]

Hi,

If the DPF is clogged, this will cause a build-up of gasses in the exhaust and in extreme cases, it will result in too much back-pressure, meaning that exhaust gas cannot be expelled from the cylinders fully (during the short window that the exhaust valve is held open by the cam shaft).

Is your DPF light constantly on?

Al.

[piotrek]

No, not even a flicker

[richardg158]

Hi, does the car seem that it is misfiring all the time or is it only occasionally? My 170 TDI, ocassionally does this for 5 minutes every 1000 miles or so when the DPF is regenerating. I normally drive in a lower gear for a few miles and it clears. Once the regeneration process has taken place it returns to normal and is fantastically smooth. If you do alot of short trips it is possible that the DPF does not get a chance to regenerate correctly, so it could seem like you have a misfire as I believe it would consistantly me trying to regenerate itself.

I must admit the first time my car did it I was ready to take it back (thought something terminal was failing!) Mine also sounds terrible whilst it is regenerating (very tractor like!) but soons returns to normal. Car has now done 25k and is fine. Must admit I did feel this was something the dealership should mention when seeling cars with these engines.

Hope this helps and it is your DPF

[richardg158]

Forgot to add - my DPF light has never come on either!

[piotrek]

Hi Richard

Thanks for the info. Sounds like the same you experince but as you say it would be good to know this in advance. I have argued with the dealer that surely Audi would do such a thing and convinced him to re-check everything again because last time they said the MAF was faulty. Will post the outcome.
Thanks again. Peter

[piotrek]

Hi All

Thanks for your input everyone. It was or is the DPF that is causing the misfire. I would have liked to have known about this at the time of buying but at least its nothing serious just irritating.
Thanks again :nervous:

[toff]

I'm so pleased I don't have one fitted to my car (sorry environment!)

Did they simply replace the DPF on your car or did they give it a good clean-out?

Al.

[piotrek]

Hi

Its not necessary to replace the DPF, just to run the car for about 15 mins over 2000rpm. So a nice run is needed to get the DPF upto the correct temperature so it cleans it's self.
The misfire or hesitation that can be felt sometimes is the ECU altering the engine conditions so it does this automatically, but of course if you are just driving around town it is more noticeable whereas on a run at some speed it is'nt.
According to the manual a warning light should come to warn that the DPF is clogged but it must be really bad for this to happen as I understand.

Regards
Peter