It turns out that the brand new 2nd plug in from the drivers side is completely black… probably since when I first connected the HT leads to the plugs, they were connected in the wrong order and when I started the car it ran rough and there was a pop from the exhaust - obviously I switched off the engine quickly and found out what was wrong.
I connected the leads (actually different ones (OEM Renault) this time) in the correct order, making sure they seated properly with a positive click.
Connected everything up again and still have the issue of the car sounding like it’s running on 3 cylinders…
Will this be because I haven’t replaced the black spark plug? I did try to clean off as much of the carbon as possible before reinstalling with some kitchen roll which did remove some of the black carbon but not all (this is because I didn’t have spark plug cleaner or anything similar available.
Do you think the plug is now the issue or could I have damaged something else?