At all speeds my 2003 Focus SE SOHC engine with 110k miles on it began
making a horrible clacky sounding noise and stalls when I try to idle
the motor.  The check engine light began blinking.  The oil and
coolant both look fine. When I pulled the plugs I noticed that one of
them had the ceramic around the bottom of the metal pole had separated
from the rest of the ceramic and slid down over the pole, but it
didn't look like anything broke loose into the cylinder. I replaced
the plugs and wires.

It sounds like all of the valves are banging around, and it happens at
all speeds.

The car was in excellent condition inside and out until this problem
happened.  I'm getting this sick feeling that I finally may have blown
my first motor.  I am still on my original timing belt.

Does anyone have any ideas on what may have happened?