car running on 3 cylinders

[derrickmd18@juno.com (der flo)]

I replaced the distributor cap today and its still doing the same thing. 
I already replaced the sparkplugs and wires.  I don't think its a fuel
problem.  when I disconnect the coolant sensor it revs two 1500RPM and
stays there.  when I try u rev the motor with the coolant sensor
disconnected it buggs down like its going to cut off.  the idle is rough
as hell.  and #4 cylinder isn't working.  I was told it might be the
coil.  does anyone have any suggestions?