Hi, for about 3 years my 500L used to have a massive pop after switching the ignition off when the engine had been running more than 10 minutes or so, the bang was so pronounced that it would frighten bystanders and the car gained the affectionate name of Poppy with our microcar club because of this. We got to wait for the bang every time I switched off. One day however the bang was extra loud and the rear exhaust pipe sheared (it was a sports exhaust but I don't know what make). I then had to buy and fit a new exhaust system and the car lost its "pop", This was quite disappointing as it seemed to lose some of its character. If your pop isn't a threat to your exhaust I wouldn't worry about it, just my opinion.

Overfuleing maybe? And when the engine stops the lack of exaust gas that's had most of the oxygen used up flowing through means the fuel in the exhaust gets enough clean air to it for it to ignite?


Highly doubtful I know but slim possiblty