Hard time starting when engine is cold, mainly over night. Engine turns over as if low compression in engine, popping is heard through intake. Car will eventually start and raw gas is smelled through tailpipe. Once car starts, it will be fine for the rest of the day or until engine gets cold. Car drives fine, no hesitation, no surging and runs good. New water temp sensor for computer was installed. Still have same problem starting in cold weather. Please advise.