Missfire problem?

[borneo]

I've got a problem with my engine vibrating really badly (still does it with the clutch depressed so I'm pretty sure it's the engine). It makes the whole car shake. It's intermitent (but getting more regular) so I'm pretty sure it can't be an engine mount. I think it might be the engine missing although the spark plugs all look to be okay and the leads are brand new. Thought it might be the ignition coil breaking down so I've got a new one of those and I'm fitting a new dizzy cap and rotor arm at the same time as they're both looking a bit tired. Does this sound about right or am I totally off the mark? Also does anyone know what the white bits, with rubber covers, that fit between the leads and the dizzy do? I've never had them on any other car. Any help would be much appreciated.

[Burns]

mate, mine's misfiring on number 3 cylinder and it has the same issue with shaking the car as you're describing?

 

are you getting a spark at every cylinder? as one of my plugs is the issue (even though they're not that old)

[borneo]

Like I said, the problem is intermitent. Never seems to want to play up when I want to check it.