I've got a small evap leak in my 08 Vic and I want to know where to start. This problem started maybe a month or two ago, however I haven't smelled any gas. I replaced my gas cap maybe 5 months ago so I don't think that would be the problem, besides id assume it would read as a large evap leak.
Did you wipe off with soap and water solution where the gas cap seals?? if not there is a plastic evap sensor thing by the booster i heard crown vics are prone to those going out.
I just fixed this on my 03 last week, i wiped off the seal spot and got a new cap been good since.
also engine lights dont go off by themselves, you have to disconnect the negative battery cable for like 2 minutes then hook it back up to clear the light then wait to see if the light comes back on.