Insignia rough running exhaust leak

Sounds frustrating! I had similar symptoms with my old Renault Megane – though it was a diesel. Check engine light, rough running, the works. In my case, it turned out to be a small leak in the exhaust system. Even a tiny hole can throw off the engine's readings and cause misfires. The Engine Control Unit (ECU) uses readings from oxygen sensors in the exhaust to fine-tune the fuel mixture. If there's a leak, the sensors might report incorrect values, leading to the ECU adjusting the mixture incorrectly, hence the rough running.

Wow, a leak in the exhaust system? I wouldn't have thought of that! Where exactly was the leak on your Megane? Was it easy to spot, or did you need special equipment to find it? What do you mean by "misfires"?

Mine was near one of the exhaust joints, pretty hard to see without getting the car up on a lift. 'Misfires' mean that one or more of the cylinders in your engine isn't firing properly, that is, the air-fuel mixture isn't igniting correctly. It's best to get it checked out by a workshop. They'll have the right tools and know where to look.

Thanks so much for the advice! I took it to a local workshop, and you were spot on – it was a tiny exhaust leak! They found it, welded it up, and the car is running perfectly again. The final bill came to 265€ which is way less than a new fuel pump! Really appreciate your help!