I'll try not to ramble. The service light on my 99 S80 would come on after start up then go off after driving it. This happened for about a week. I drive it to work and it's business as usual. Start it to leave at the end of the day and it has a very uneven idle, no power it would just barely creep at idle. Tried to rev it in neutral and it would only go to 1800 rpm. Warning on dash said "engine systems service urgent". Had it towed home. Tried it the next morning and it's even rougher will barely rev past 1000 rpm, and can smell rich exhaust fumes. Any advice?