I often get a whiff of rotten eggs from my 2010 BMW 335i. Any suggestions?
RM, Eaglescliffe, Co Durham
The rotten-egg smell is almost certainly sulphur, which is an ingredient in petrol, and it is probably coming from the catalytic converter. The job of this device is to convert exhaust pollutants into more or less clean air, and the process can produce a sulphurous smell from time to time.
If there’s a problem with overfuelling, there will be more exhaust gases than the component can deal with, which is when the stench becomes persistent.
Have the emissions tested to check whether too much fuel is being fed through the engine. If it is, your car will need a diagnostic test to find the cause of the overfuelling.
Dave Pollard has written several Haynes manuals and has tested just about every car-related accessory — read more from Dave here.
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