I've got an '02 Disco with 124K miles on it. It has a misfire in cylinders 3 and 4. The car also has trouble starting. It will struggle and fail to start then after a second attempt it will succeed. Sometimes it will start in one go but it feels like a long time and it struggles mightily. Does anyone have a suggestion for how to proceed on resolving the misfires? I'd love some advice because I don't actually have tools to check the vacuum or fuel pressure and I'm a little bit of a novice. Should I start with the fuel injectors or go out and get those pressure checking tools? Does anyone have a read on some likely culprits here?

Here's all the info that I have:

- It had a random misfire, cylinder 4 misfire, and o2 sensor codes.
- After changing the plugs and o2 sensors, it now has cylinder 3 and cylinder 4 codes (random misfire code not present for now after idling for about 10 mins and reving engine).
- After getting the old plugs out, they had plenty of spark left (about .042" gap) which is like-new condition.
- The right side (passenger in US) plugs (#2,4,6,8) were all black and dry.
- The left side spark plugs normal (#1,3,5,7) with tan-colored tips.
- Plug #4 might have been oily, but I cleaned it before investigating fully and I can't recall if it was the threads or actually the whole head. This was before I thought it check the condition of the plugs and was just trying to clean and reinstall. Most of my mechanicing has been on bikes so yeah. Some things don't translate.
- The spark plug wires look new, not original. They're blue like the British Atlantic ones and they had fresh dielectric grease in the boots.
- I cleaned the PCV valve, which was crusty and full of gunk but not occluded. (The oil separator is missing though).
- I checked the alternator and battery, both are fine.
- I checked the air filter and cleaned the MAF (both were clean to begin with).
- I checked for loose hoses that I could see from above and tightened down a couple in the air intake assembly.
- New o2 sensors are functioning normally.

Here's some photos of the spark plugs:


Sorry I didn't include #6, it looks the same as 2,4,8

#4

#3

#4 again