Hi. Car is 23 months old, c13k miles. Main dealer supplied. It has developed an apparent misfire when starting from cold - engine runs rough, reduced/no power for 30 seconds/a minute. All then OK. Main dealer says this is a characteristic of this particular engine which has a built in system to bring the catalytic converter up to operating temperature quickly when the coolant temperature is below 10C. This results in the roughness I am experiencing. This doesn't sound plausible to me and I wonder if I am being fobbed off. The roughness was not apparent last winter when the car was new but has developed recently. I would welcome your thoughts.