I have a problem with my Ford 200 F150 4x4 5.4L upon start up. It has happened to me twice now, but about 2 weeks apart. I turn the engine over and the the truck just vibrates like crazy for about 10 seconds or so. ( I have to get out to close the gate at my home) at that point I notice a STRONG gasoline odor. But otherwise all is fine. Truck runs good with no further problems. Any ideas anyone on what I might be experiencing?

 

Hi and welcome to the forum.
I would try cleaning the mass-airflow sensor first. My Windstar will do this when it gets dirty.
Jimmy