Renault Spider Misfire Cylinder

I think I can help. I had a similar issue with my Spider, although I didn't have the reduced engine power. Rough idle and misfires are a pain, that's for sure. Have you checked the fault codes? Mine was throwing codes related to cylinder misfires too. It's worth checking which cylinder is misfiring. Did you consider the ignition coils? They sometimes cause similar problems on the Renault Spider.

Thanks for the quick response! Yes, I did hook it up to an OBD scanner, and it's showing misfires on cylinder 3. I was leaning towards a faulty injector on that cylinder, but your mention of the ignition coils has me thinking. Is there a way to test them without just throwing parts at the problem? I really would like to nail it down before ordering parts. Did you figure out on yours what was the source of the misfires and rough idle?

Okay, misfire on cylinder 3 points towards either the injector or the coil pack for that cylinder. You could try swapping the coil pack from cylinder 3 with another cylinder (say, cylinder 1) and see if the misfire moves with it. If it does, then it's likely the coil pack. Otherwise, injector is the next likely culprit. In my case, it ended up being both the injector and the coil. If you are not comfortable doing this maybe it's time to visit a workshop?

Right, thanks for the advice, I'll try swapping the coil packs around and see if the misfire moves. If not, I guess it's a new injector for cylinder 3. I took it to a workshop. They confirmed it, plus labour, all in all I'm looking at around 515€. Appreciate your help!