Generally a spark plug won't fail like that, they wear out and over time the idle usually will gets worse, not miss-fire under load.

An ignition lead will cause the missfiring, they start arcing and are usually the culprit.

If the ignition lead had an open circuit the miss would be constant.

A decent mechanic at your dealership should be able to locate the fault for you and it should be a fairly quick fix.

Dizzy...hahaha...lol