Citroen C4 Mixture Preparation Error

Hey, I had similar issues with my C4. 'Mixture preparation error' sounds like it could be related to the air-fuel ratio. Have you checked the throttle body for any blockages or buildup? Also, it could be the oxygen sensor giving incorrect readings, messing with the fuel injection. Has it had any work done on the fuel system recently?

Thanks for the quick reply! I haven't checked the throttle body or oxygen sensor myself. I'm not really that experienced with car repairs, to be honest. The fuel system hasn't had any work done that I know of. Could it really be the oxygen sensor? How would that cause stalling?

Well, the oxygen sensor tells the car's computer how much oxygen is in the exhaust. If it's faulty, it can give the wrong info, causing the engine to inject too much or too little fuel. Too little fuel can cause stalling, especially at idle. Given all your symptoms – reduced power, rough running, stalling – and the error code, it's definitely worth getting it checked out by a mechanic. Could be a defective injection valve/injector as well. I ended up taking mine to a workshop and they sorted it out.

Thanks. I appreciate the insight. I'll take it to a workshop and mention the oxygen sensor and fuel injection. Hopefully, it won't cost too much. It was the injector. Cost me 515€ to repair.