Nissan Note high fuel consumption starting issue

Higher fuel consumption and poor starting definitely point towards a potential air/fuel mixture issue. Given your mileage, a defective accelerator pedal module could be the culprit, messing with the throttle valve position. The ECU relies on accurate readings from that module to control the engine idle and overall performance. Have you tried cleaning the throttle body? A build-up of carbon deposits around the throttle valve can cause similar symptoms.

Thanks for the quick reply! I haven't tried cleaning the throttle body yet. Is that something I can do myself, or is it best left to a professional? And how would I check the accelerator pedal module?

Cleaning the throttle body is doable yourself with some carb cleaner and a brush, but be careful not to damage any sensors. There are plenty of tutorials online. As for the accelerator pedal module, that's trickier. You'd need a scan tool to read its output and see if it's within the proper range. Honestly, with these symptoms, and not wanting to risk damaging anything, I'd recommend taking it to a trusted mechanic. They can properly diagnose the issue and pinpoint the problem. A defective accelerator pedal module is a plausible explanation for the elevated fuel consumption, and the starting issues too.

Thanks a lot for your help! I took it to a mechanic, and you were right. It was indeed a defective accelerator pedal module. They replaced it, and it cost me around 205€. The car is running smoothly now, and the fuel consumption is back to normal. Appreciate the advice!