Im posting this on behalf of my internetless friend.

He has purchased an 06 plate diesel octavia which is being used as a taxi. Its the sport diesel (not the VRS, but not the base model).

He is over the moon with the cars spec/space and performance, but on the odd occaision the car is left overnight and is allowed to get cold it is a nightmare the following morning. it will start on the button, but when you try and accelerate away the vehicle runs really rough and struggles to pull away this is accompanied by a lot of black smoke. as soon as the car reaches operating temperature it is perfect and the fault only returns when it stands overnight.

Initially this was accompanied with the engine management light coming on, so a visit to the local specialist revealed the (cant remember the exact name!!) valve needed replacing. This was changed (£300 worth) and the light stayed off. Problem solved we thought!!!! but no, as soon as the car sat overnight the fault returned without the management light. another diagnostic check has revealed no faults, so we are at a loss!!!!!

any help, or advice greatly appreciated

Ian

There is also another thread about this:

http://briskoda.net/octavia-ii/cold-start-hesitancy/118316/

Hope it helps.