I know this is an old thread but I had a recent issue with this and couldn't find the information below anywhere so thought it worth posting.
So the engine started misfiring on my 1.6 mk2 focus zetec and it was registering fault code p2300 (no other fault codes). I was advised I needed to get a coil pack so dutifully did this and the issue went away for a couple of days, then returned.
Initially I thought, like so many, bad coil? But something didn't add up. I checked around various forums and found lots of people saying they had replaced the ignition leads and spark plugs at the same time as the coil, but I didn't want to do this only to find I continue to have the issue so decided to do a bit of investigation myself..
So I reflected on the fact that the new coil had worked for a couple of days and figured it must be something to do with whatever had been done when the coil was replaced. So I retraced the steps for replacing a coil which led me to standing over my engine as it ticked over (lumpily) and wiggling the connector that attaches to the side of the coil. When I wiggled it, the car almost stalled. I tried it again - same result. So I figured it must be something about disconnecting and reconnecting this connector that had meant the new coil had worked for a little while.
So I did a bit more online research and found out that its not uncommon to have issues with this wiring connector and that ford now do a pigtail for this issue. So I contacted my local Ford dealer for a price for one but he had no idea what I was talking about. All I could find online was the US part number but he still couldn't figure out what I was asking for.
So I then started looking through a catalogue of connectors for the mk2 focus and about 20 pages in I found the offending item. I then went searching online for it and managed to find an original ford one for £5.36, so I ordered it. I managed to avail myself of some wiring from another vehicles wiring loom then set about soldering the wires into the connector then connecting the new connector to my existing loom.
Once I got the old connector off it became apparent what was at fault. Clearly the previous owner had one of the pins in the connector repaired and whoever did it put the pin in upside down and as a result could not push it fully home - so it was sat back from the other two connections in the connector.
Now presumably the previous owner had this repair for the other common problem on a Focus in that the wires to this connector are quite tight and prone to breaking/solder breaking in the plug connector.
Anyway, having fitted the new connector the car has never run sweeter.
Therefore my advice to anyone who suffers this same misfire issue is, before you rush out and buy a new coil, ht leads and plugs, have a little bit of an investigation of the wiring and, in particular, this connector. It could save you time and £££'s.
if the plugs at fault the resulting misfires knackers the coils and leads anyway so either way a new coil pack is required im afraid leads you can sometimes get away with but yes the wiring is very tight and hardly surprising it pulls on the connectors to be honest
That's what I thought initially but wonder if that's only the case if you run it for a significant period of time like that. Once mine started to misfire I stopped using it so I didn't think it could have knackered the coil unless the previous owner had run it for a time like that. In fact to test my theory I put the old coil back on after my repair to the connector and that seems to run fine too. I am back on the new coil now just in case but I guess my question now is could the old coil actually be ok? Or could it be knackered but just not exhibiting any signs?