I've had this car less than a week. Less than 100 miles. Today when I got in it ran rough, the check engine light started blinking and the EPC light came on. CEL went solid and I drove to the dealership (2 miles). It's a cpo with another 6 months on the factory warranty (plus the 2yr cpo).

The tech came back with a report of a fouled plug. It was replaced and everything appears to be normal.

My question is, what would cause a fouled plug? To me, it seems, there may be something else wrong that fouled the plug. Do I need to wait for another CEL to have them look closer?

When I first test drove the car it had a slight stumble at idle, which disappeared after 20 min of driving. I insisted they looked into it. Their techs said it was bad gas and put in some kind of additives. After that it was smooth as butter.

Thoughts? Opinions?