Normally, when you fill the gas tank and it's almost full, the feed clicks off. In my car, it keeps clicking off from the very beginning of the fill and even spits gasoiline back through the opening. No matter how slowly I feed the gas, it keeps kicking off, taking about 20 mionutes to fill it. Brought it to a mechanic, who cleaned clogged charcoal filter, but problem is unchanged. Also have had several "check engine" warnings that were linked to gas cap. It's been changed also but both problems persist. Any thoughts?