I this problem on my 98 (2.0L Zetec), when I used aftermarket plugs, double platimum Autolites and Bosch. I put in the stock plugs and the problem went away. These cars are VERY sensitive to the wires and plugs used. The stock plugs have a very thin center electrode, unlike the aftermarket plugs. Supposely this enables them to fire with less voltage. Whatever! THEY WORK FLAWLESSLY!
