I had to run an errand on my lunch just now, and halfway up the highway my engine started missing. At idle it runs really rough, and the engine light has blinked a few times. How likely is it that I fouled a plug? I know the stock ones are reportedly junk, but I've never had one give out like that. Any suggestions for a decent plug that my local parts store will stock? The car has 52k miles on it. Thanks, Steve