Hi guys, wondering if anyone can help....

My Fiesta (1.25 Zetec), it started about 3miles away from home, just a slight misfire at about 3000rpm, it also stutters when pulling away at about 1200rpm .

Phil has taken the plugs out and found No4 to be all coked up, cleaned it up, refitted closing the gap slightly and no difference, replaced the plug for another, no luck, still there.

Guessing its probably the lead? Its coilpack, and the missfire is only affecting one cylinder, so I am guessing the coilpack is fine, as it'd affect two if it was broken?

Any help appreciated, thanks guys