Anyone have any issue with engine backfire on cold startup? C400 is 8 weeks old, and at 3 weeks started to backfire in the engine compartment, not the exhaust, approx 2-8 times, and idle's around 1,300rpm. Engine sounds a little rough when idling. The problem goes away after engine warms up - runs smoother then, and idle's around 700pm.

 

Did you find a resolution to your problem?

 

The engine can be less than smooth till the engine reaches 80C. Its completely normal. I dont warm up the engine, simply drive conservatively till it reaches normal operating temp. Never had any problems except the almost imperceptible lumpiness till warm.