Volvo S40 2005 Diesel
Occasionally after starting the car it feels like the engine is struggling, does not work properly and black thick smoke and soot is coming from exhaust. There is no problems with staring, car starts easily. But engine works unevenly and feel like it is stalling.
Usually when I have this kind of start I shut it off as fast as possible and after restarting everything is fine – no smoke, nothing (except the engine warning symbol wont light in the dashboard before the restart).
Also:
1.Never have this problem if the car has not driven for a while (more than 4 hours)
2.This is not a regular thing. It can be weeks without this bad start. But sometimes it happens few times a day.
3.Car always works after restarting. Never had bad start two times a row.
4.Car has its second engine now. This bad starting thing happened with both engines. Except the first engine did not have the thick smoke.
I have no ideas where the problem could be? Is this electrical problem?

 

Is this a UK model? Not trying to run you off but look at the UK Volvo forums for better help.
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Mostly North American version owners here and we would have a hard time figuring out a diesel engine.