Touareg 7P 3.0 262ps rough idle

[WSpence72]

Evening all,

I'm hoping for some help diagnosing the lumpy idle in my '15 VW Touareg running the 262PS 3.0 6-cyl Audi engine, at 50k miles.

The issues started a few months back and consist of slight rough idle at start up (needle doesn't jump wildly, but vibration noticeable); occasional slight burnt diesel fuel smell at start up; slight dip in power at the 1400rpm mark; "pinking" on heavy acceleration but running smooth once up on cam. It is a constant problem, however is at times more marked than others - i.e can be running quite rough through the city, then when Stop/Start kicks in at lights after restarting it's calmer.

Diagnostics flagged code P030300 - misfire in cylinder 3. I took the car to a diesel specialist to strip the injector and he found it to be leaking excessively. The copper washer had vaporised away, and the only seal was formed with carbon build up. Unfortunately a new injector didn't clear the issues so they kindly refurbed the old injector and reinstated.

The new injector was bench tested and found to be good (so this wasn't the problem); a cylinder leakage test was undertaken and scored 96% - sound, in their opinion. This meant that they were running out of ideas - suggesting the possibility that some carbon had dislodged, detonated and triggered a mild deformation of the con-rod. I'm not ruling this out, but it seems like quite a remote possibility (?).

Before i get into the expensive of tearing the engine down i was wondering whether anyone has experienced anything similar and can suggest other areas that i can investigate?

In terms of other observations: no noticeable exhaust smoke on start up; no oily blow out residue on any of the manifolds around the crank case; EGR and airflow are a bit mucky - i opened up and de-coked air pipe but not sure if this would impact mix at low revs?

Thanks,

[Crasher]

Suggests to me that the injector set face of the head itself is damaged.