The idle on my 2001 Expedition 4.6L goes up and down between 500 and 800 RPM
quickly when in gear like at a stop light.  When it is in park it idles just
fine.  I just put new plugs in it.  This problem existed before the new
plugs along with some other issues.  The other issues went away while this
one did not.  I did notice when I changed the plugs that one of the coils
had a different ohm reading than the rest.  Seven of the coils had .1 ohms
and one had .22 ohms.  Could this coil be the problem.  The service engine
light is not on.