Mercedes C Klasse cold start issue

I had similar cold start problems with my Mercedes C Klasse. Rough idle, poor starting, the whole shebang. Have you checked the fuel pressure regulator? A malfunctioning regulator could cause fuel starvation during cold starts, mimicking injector issues. Also, what's the condition of your fuel filter? A clogged filter can restrict fuel delivery, especially when the engine is demanding more fuel during the cold start enrichment phase.

Interesting points. I hadn't considered the fuel pressure regulator, I was so focused on the injectors. Where is the fuel pressure regulator located in your Mercedes, and how involved was it to check? The fuel filter was replaced about 30000km ago during a service, but I suppose it wouldn't hurt to double-check it. The regulator is my primary concern now, based on your response.

I didn't check the fuel pressure regulator myself. I took it to a workshop. They ran diagnostics and pinpointed the issue pretty quickly. It could still be the injectors but if you lack the gear to properly diagnose it I would take it to someone who does. I have proper diagnostic equipment, but diagnosing fuel injection issues can be tricky without the right tools. Better to get a proper diagnosis before you go replacing parts.

I took it to my local shop. Turns out I was right. It was the fuel injectors, but not all of them. One was definitely shot. I replaced the faulty injector and the car is now running smoothly. Total cost was about 515€, parts and labor. Fuel delivery is now spot-on, and those cold start problems are gone. No more rough idle. Thanks again for pointing me in the right direction!