C4 Diesel Fuel Pressure Issue

Sounds frustrating! I had a similar problem with my old Renault Megane, also diesel, after a fuel filter change. Check engine light, rough idle, the whole shebang. In my case, the error code pointed to a fuel pressure regulator issue. The fuel pressure regulator’s job is to maintain a constant pressure in the fuel system. A faulty regulator causes an imbalance, resulting in either too much or too little fuel being delivered to the engine. Did you happen to notice any error codes when the light came on? It could be related.

That's interesting! I did see something about 'fuel pressure' when I scanned it with my OBD reader, but I didn't think much of it. The code was something like P0087, 'Fuel Rail/System Pressure - Too Low'. Could that really be the fuel pressure regulator, even after just a filter change?

Yep, P0087 definitely suggests low fuel pressure. It's possible the filter change disturbed something, or maybe it's just coincidence and the regulator was on its way out anyway. Either way, that code, combined with your symptoms, strongly points towards a fuel pressure regulator problem. Best to get it checked by a professional. They can properly diagnose it and confirm if the regulator is indeed the culprit. Ignoring it can lead to more serious fuel system damage.

Thanks for the advice! I took it to the shop, and you were spot on – fuel pressure regulator was defective. Apparently, the error was registered after changing the fuel filter. Cost me 45€ to replace it. Runs like a charm now!