I had the "check engine" come on about a week and a half ago, it said cylinder 8 misfire, so i replaced all the sparkplugs and discovered that the prong at the end had broken off. After, the "check engine" light went off. Then yesterday the "check engine" light came on again and said the same thing, the guy at Autozone said that it can sometimes show the same problem when there isn't a problem, said that the computer has not reset iteself yet, so he erased the code and now the "check engine" light has not come on again. Is what he said right???

Thanks