Mk2 1.6 - Misfire At 2K

Hi all

I'm now a few weeks into being a Focus owner and think I have come across one of the apparently common problems, a misfire at around 2k revs when in second or third gear.

Anyway, I grabbed 5 minutes yesterday and took a look at the HT leads and plugs to see if they were sitting in water. Plugs 1 & 2 were dry but had a coating of orange coloured dust on them, I assumed it was rust as could see signs of it around the plugs. Plugs 3 & 4 were both surrounded by gunky liquid (plug 4 had gunk on the thread too) and the ends of the HT leads were wet.

I had a poke around with an old cloth and a long screwdriver and the gunk/liquid appears to be a terracotta colour and definitely not just rusty water. To my untrained eyes it looks more like coolant that has seeped into the area from near plugs 3 & 4. I am sure I read somewhere that the known problem with water leaking into that area can cause the core plugs to corrode, could this by the cause of the coolant leak? If so, is there a guide somewhere on how to fix this?

I have a new ignition coil and leads but am hesitant to fit them until the problem is sorted, just in case the liquid causes damage and costs me another small fortune in parts!

The other thing I noticed was that there were two holes in the rocker cover, one that is threaded and the other sits in between the access holes for plugs 2 & 3. Should these be covered/have something in them? The bigger holes had remnants of silicone around it so I'm not sure if there is meant to be a bung in there.

Any help/advice would be much appreciated.

Thanks

Olly