Thalia Misfire Exhaust Leak

Uneven running and a check engine light could be a few things, but an exhaust leak is plausible. I had similar symptoms on my old Opel Astra: rough idle, hesitation... Have you checked for any obvious hissing sounds around the exhaust manifold and pipes? What error code is it throwing?

No hissing, but I haven't had it on a lift to check thoroughly. The error code points towards a misfire. Could a small leak cause such noticeable misfires? Ignition coil and spark plugs are new.

A leak that close to the engine could definitely mess with the O2 sensor readings and cause misfires, especially under load. If plugs and coil are new, vacuum leak and exhaust are possible. I would take it to a workshop if you don't have the tools and space to inspect the exhaust system.

It turned out to be a crack in the exhaust manifold, just before the catalytic converter. Repair cost 265€, and it runs smoothly now.