Go here:
http://www.peachparts.com/shopforum/showthread.php?t=107630
Build this LED tool and go to pin 8 for codes . If a coil is suspect , you should see a code 21/22/or 23... one code for each coil..you can then move the coils location and see if the code follows the offending coil.
More likely it just needs a good drying out...