One problem related to engine noise has been reported for the 2013 Mercedes Benz C250. The most recently reported issues are listed below.
2014-08-engine light came on, vehicle would not accelerate past 80 km/h and the engine shut off - driving in traffic. 2014-08-brought vehicle to 550 terminal avenue. They said it was just the fault-pump and that it was safe to drive. They advised me that they had to order the part from germany. Vehicle was later returned the same day. (23505 km) 2014-08-the vehicle engine shut down while driving out the drive way, so I had it towed to 550 terminal avenue. (23514 km). They replaced a throttle actuator. 2014-08-vehicle was ready for pick up. Vehicle would not start. Battery replaced. 2014-08-picked up vehicle. Then experienced a low accelerating after braking. Went with the foreman for a road test and he agreed that there was a delay when accelerating and that it felt like its going to stall while in "drive". 2014-08-they said it was caused by 13 % ethanol in fuel/ software. There's a pinging sound. But I buy the same gas every time 94 octane from chevron. I had a verbal agreement saying that my car was safe to drive and for me to come back to Mercedes Benz with a new tank of gasoline to see if I would still have the same issues as it was stated that the issue may have been cause by using gas with 13% ethanol/software.