My good old TDV8 3.6 (2007) received a new set of AT tires last summer (275/55 R 20) which have a 6% bigger circumference than the original tires. Looks great, wheelhouses are filled better and only minor works in the rear back wheelhouse had to be done to avoid rubbing. Also, to follow the regulations in Germany, the speedometer had to be adjusted, so it correctly indicates the driven speed (without that it would show to little, which is forbidden here). That wasn’t a big deal nor cost. Comfort is very good, though I have the impression that the engine must fight a lot at low revs against the higher torque requirement of the bigger wheels to get the 2.7 tons moving from stand. At higher speeds the lower revs are making the ride even smoother.

I use the RR mostly in the woods and off-road (hunting) and rather drive low mileage distances. The AGR (German term, I guess something like exhaust gas regulation valve) has been changed about 10.000 km ago, so I know I need to take a tour on the motorway regularly to prevent coking.

This just as a background, potentially it could have an influence on the current challenge …

To the matter: Since a few months I note a strange almost flabby effect in the gearbox when accelerating from around 2,000 to 2,500 revs. It feels like the engine has difficulties accelerating and doesn’t have enough power. At night, when there is someone behind me with the lights on, I note there is a bit white smoke during that revs. At daylight, I can't notice that. However, it seems different to when the AGR had to be changed. There was no power loss back then and it produced lots of black smoke.

Changing the gears manually helps because the gearbox seems to want to keep the revs in this band. I also tried to rev the engine in Neutral – there is no effect then! It only appears when driving and torque is required.

Since a few weeks now, about 10 - 20 secs after starting to drive, a double “ding” rings and it shows “Engine System Fault”. When starting the engine without immediately starting to drive, the message first appears after starting to drive. The message disappears after a few sec and the RR drives on without going into slow mode. The flabby feeling between 2,000 and 2,500 revs remains. Also, to rev in the stand does not cause the double “ding” to appear.

Overall, gas consumption is up slightly since the problem exists.

I read the IID codes and it shows P132B “Turbolader Boost-Regelung A, Betriebsverhalten” (don’t know what that error code would be in English, literally translated it is turbocharger boost regulation A, operating behaviour).

Does anyone have a clue what the cause could be?

I found three potential cures so far, reading the net:

- Changing the two thick air intake tubes because of potential cracks (might this cause the white smoke?)
- The turbo actuator might be stuck, so trying to free it using a hanger and WD40 plus oil afterwards (Don’t know how to access the actuator, can anyone describe that? And, can this be the problem as the engine revs without any problems in Neutral?)
- Using a cleaning fluid called “Revive turbo cleaner” might help clean the air system from inside (might be nonsense as a cure)

Any comments on these? Can the gearbox be the problem? Changing the oil there is expensive and the gears shift ok as far as I can tell.

Thanks for any helpful comment on this!

Sounds to me most likely place to start is your right hand side (as you sit in drivers seat) turbo actuator. These can stick. There are a couple of threads on here on how to check/free off if stuck and lubricate.
Basic access is through wheel arch and underneath the car. It is not that difficult. You can hear/see the actuator going through initialisation cycles at ignition on and after the engine is switched off. Previously a 2008MY Tonga Green Vogue SE 3.6 TDV8