Originally Posted by martysmartie

It may well be a coil pack as these are prone to failure on modern cars.

However, the fact it's misfiring on one cylinder would lead me to question this.

The coil is essentially a transformer, which is what generates the high voltage required to create the spark at the plugs, it's named so as it is two coils in one.

One for two cylinders, therefore in theory cylinder four should be misfiring as well.

It may be something mechanical on that cylinder that is causing the misfire, but you need tools to verify this.

Martin