Hello, 1st time user... I'm the original owner of a 1997 Lariat F-150 5.4L. It has 150K miles. My truck cranks and turns but does not fire, after the 1st crank. On the second crank a very loud backfire, (gone thru 2 mufflers already). Usually starts on the 3rd crank. Only happens during 1st start of the day. It's fine the rest of the day.