smoky exhaust

Hi I had the management light come and and O2 sensor was the problem . It was reset waited it went about 3weeks came on so booked it in for change also had the timing belt changed at the same time all done today .Prior to this the car was running fine .Drove home about 15 miles car seemed fine and as I backed up the drive saw black smoke at the back .Question is there anything the garage may not have done properly to cause this . This beast has and is costing me a fortune and not being too mechanical will have to take the garages word for what the new prob is which no doubt Wont be theirs 1999 V70 AWD automatic 60 K Thanks for any advice

Potentially it was not the O2 sensor at fault. A vacuum leak can throw an O2 fault symptom. Check all your vacuum pipes and hoses on the intake side of the engine.

Thanks But why would it smoke now after the sensor change? whenit never before Not doubting your info just tryign to get facts to confront the garage if need be

Black smoke is usually caused the car running rich you maybe just blowing the soot out of the exhaust. (Especially if the vehicle is only used on short runs and rarely warms up) If you take it for a thrash and you still get bad black smoke and rubbish economy then it's a fuelling issue. rule of thumb, somewhat general Blue smoke - burning oil - bad turbo, failing head gasket, valve seals white smoke - leaking coolant - head gasket failure, not to be confused with the vapour seen as a car warms up black smoke - way too rich, faulty injector, bad sensor(s), sooty exhaust malc

....is your car getting up to temperature? I'm thinking faulty thermostat now.

Thanks guys yes the car is up to temp it was running fine and clear prior to the sensor change

there are two sensors on the 850 were both changed, were they propper volvo items or not I am inclined to think the new sensor is faulty, I have had previouse problems with after market lambda sensors they do not do the job properly. laurence :animal-smiley-037::animal-smiley-037::animal-smiley-037:

Laurence you were correct the new sensor was faulty so the fitted another New one and touch wood seems fine

What a rich vein of knowledge this site is.Well done everybody,I will no doubt be testing your brains myself and Im sure you,l sort it out Regards Mick.