Hey everyone,

I have recently noticed a couple problems with my F55 Cooper S JCW kit. When I coldstart the car, 8 times out of 10 the car would start pop and banging - a feature that is evident in the jcw model but not the cooper s variant. Another issue is that, more evident when the engine is cold, the car is really jerky at lower speeds, especially in sport mode. But sometimes it feels like it just has these weird but not too extreme lags when changing gears. I am not sure if these two problems are directly linked to each other.

The car power wise seems alright, maybe acceleration with lower throttle might be a bit off but not 100% sure, fuel economy appears to be normal and in-line with previous years and there are no errors popping up. I would have assumed it might have been the spark plugs but not too sure with the good fuel economy and no check engine lights.

Maybe someone has a better idea what might be the issue?