My 405 1905cc petrol engine smokes badly from the exhaust (black smoke), especially when cold. What is likely to be the cause of this?
A. The most common cause of smoke from this engine (and also 1600cc as fitted to 205 GTi, 309 among others) is worn valve stem oil seals. These stop oil from the cylinder head passing down the valve guides and into the combustion chamber. When they wear and/or perish, oil can pass them and is then burned with the combustion mixture, causing black smoke. The seals are only about 80p each, but the job entails removing the cylinder head for a rebuild.
