Unusual Engine Starting Problem

[V1]

Every time I re-start my engine while it's still hot, it has some problems. The engine fires, but then stumbles at 200-300 RPM for about 2 seconds before jumping up to idle. I catch a whiff of exhaust from the engine bay every time this happens. Otherwise the car has no CEL's, makes no noise, and it runs as good as new.

Here is a synopsis of my car's recent maintenance history:
-Discovered strong fuel/exhaust smell coming from the engine bay
-Found 3 looose spark plugs (NGK)
-Cleaned & tightened NGK's; smell went away
-Immediately had problem described above as well as poor gas mileage
-Replaced NGK's with 6 new Motorcraft plugs
-Mileage improved significantly, but
-Engine starting problem came back 2 days later

My greatest fear is that the cylinder head was cracked by the loose plug condition. Either that or the threads were damaged. What else could it be? Cracked exhaust manifold?

I'm going to visit an engine shop today to ask them. In the meantime, any constructive feedback would be really great. Thanks in advance.

 

[PT1]

Start it in a dark garage and see if you have an arcing plug wire(s).

 

[road_rascal]

Vapor lock? The ethanol fuel makes my van act a little wierd on hot restarts once in a while (especially after a long highway trip, shut off for refueling, then restart). No codes, no pending ODB2 codes from the scanner. Doesn't do it all the time. So I'll assume a slight case of vapor lock.

 

[Merkava_4]

+1, I was thinking it could be vapor lock too; especially if you've got low fuel pressure. Sometimes these fuel pressure regulators need replacing.

 

[mechtech2]

My first guess is a bad fuel pressure regulator.
Smelling gasoline is never acceptable in a vehicle.
It may also be in the evaporation/vent system.

 

[Smoky14]

Injector may be leaking down when setting.