S40 Poor Starting Reduced Power

I also have an S40. Your symptoms sound extremely similar to what I experienced last year. Did you notice any black smoke or a strong fuel smell along with the poor starting and idling? My mechanic initially suspected a faulty sensor, but it turned out to be a clogged fuel injector.

Thanks for the quick reply! No black smoke, but there's definitely a stronger fuel smell than usual. You mentioned a clogged fuel injector. How did you determine that was the issue, and did you try cleaning it before replacing it?

My mechanic used a diagnostic tool to check the performance of each injector individually. Apparently, one wasn't spraying fuel correctly. He did try cleaning it, but it didn't solve the problem. He advised that replacement was the best course of action to ensure consistent fuel delivery and prevent further engine damage. Given your symptoms, I would recommend taking it to a workshop to have them check the injection system. It is best to be sure!

Thanks for the advice! I took it to the workshop, and you were right – a defective injection nozzle was the problem. The estimated repair cost is 515€. They're replacing the faulty nozzle now. Hopefully, this resolves all the issues.