Kalos engine running rich

I had a similar issue with my Kalos. Those symptoms sound familiar. A rich mixture can stem from various things. Besides the injectors, have you checked the catalytic converter, spark plugs, and air filter recently? A clogged catalytic converter can restrict exhaust flow, causing the engine to run rich. Similarly, fouled spark plugs might not ignite the fuel efficiently, leading to unburnt fuel in the exhaust. A dirty air filter restricts airflow, which will impact the fuel/air mixture. Did the check engine light give you any specific error codes?

I don’t have the error codes. But are you suggesting the catalytic converter, spark plugs, and air filter, if faulty, could directly cause the engine running rich, or are they potential consequences of the rich mixture?

I'm saying they can cause the rich running condition. Think of it like this: your engine needs the right balance of air and fuel to burn efficiently. If the catalytic converter is blocked, the engine can't 'breathe' properly, and the mixture gets thrown off. Same with a clogged air filter - not enough air gets in, so the computer compensates by reducing air and/or increasing fuel to maintain the desired ratio at all times. Honestly, given the symptoms and mileage, it's best to get it properly diagnosed by a workshop. They'll be able to pinpoint the exact cause much faster than you can by yourself.

It turned out to be a defective fuel injector as suspected. The repair, including parts and labor, was 515€. The car is now running smoothly again. Thanks for the insights.