2008 Taurus X, misfire / SES light flashes

All,

I've got a 2008 Taurus X with 108,000 miles. Intermittently, there seems to be a misfire under light acceleration and the SES light will flash. There aren't any codes picked up by a pocket scanner and the SES light is not permanently lit, only during the miss.

From the research I've done, this problem appears to be related to the coils. The dealer we bought from last year claimed they changed the coils before it was sold, but I suspect they probably only changed the front-most (easy to get to) coils and left the rearward ones as-is.

Any way to diagnose which coils need replacement?

Go to Auto Zone or Advanced and get a computer scan done it should pinpoint the cylinder misfiring.

http://www.ebay.com/ search 231666763920 The tester will show a blink if erratic you found the cylinder.
Go to Auto Zone or Advanced and get a free scan it should point to the problem cylinder.
A injector can also cause a misfire.
Get a noid light at parts store to diagnosis a a bad wire.
Put a long screwdriver to top of injector and listen.