We took delivery of a new Mercedes E350CDI Coupe Sport 2 months ago and have completed 2,000 miles. We choose it in comparison with the equivalent BMW and Audi Coupes based on an overall mix of ride, performance, classier exterior, particularly with the panoramic roof, and perhaps surprisingly, the Merc's value for money. Overall it's going well averaging 42mpg and 52mpg on longer runs including a fair bit of urban motoring. We have just one aspect on which we would appreciate your advice: On 5 separate occasions, usually 7-10 days apart we have noted a very hot smell outside the car around the bonnet area - no smoke and in ‘Comfort’ auto mode, tickover rises from 650rpm to 850rpm, while the automatic transmission changes up at around 2,100rpm instead of 1,650rpm. Having parked up for a few hours and re-used, the symptoms completely disappear. The dealer has checked out all the engine and gear box diagnostics and everything seems to be normal. He says what is happening is the engine management system is running a refresh programme for the particulate filter. What do you think is going on?