When start car loud pop noise then when driving a rattl from exhaust but not all the time.also smell from back of car when ive parked up. 1.2 fiat punto 52 plate.?

The loud pop noise when starting your Fiat Punto could indicate an issue with the ignition system or an exhaust leak. The rattling noise while driving suggests that there may be loose components in the exhaust system, such as a heat shield or a damaged muffler. The smell from the back of the car, especially after parking, could be due to exhaust fumes escaping or an overheating issue. It's advisable to have a qualified mechanic inspect the vehicle to diagnose and resolve these problems.