I don't know what he meant by upper gasket as I am not knowledgeable about cars at all. He couldn't reproduce the problem ever and no codes ever showed up. The check engine light used to come on but no codes showed up. Last year it used to stall when I came to a stop but always started back up. Now it's not stalling except once when idling for a few minutes. It's just not starting after driving it for a short distance, then starting it up after it being shut off for a few minutes. It always starts after about 30 min.