Hi there, Dunno if this is relevant, but just a thought that sprung to mind. I don't know if it's relevant to Volvos, but being the enviro - wagen that they are, maybe. The Mercedes 220 Diesel suffers identical symptoms, due to a thingy called a 'recirculation valve' not working. Basically it sends the exhaust fumes back through for a second burn, and if it doesn't work you get thick black smoke out of the exhaust. Perhaps a Tecchie on the site can advise if your car has a similar setup? Regards, Anthony.