Howdy neighbor, first thing you need to do is get a scan test performed to pinpoint the trouble! Too many possibilities for the misfire. While i agree with the first answer in part, these engines are prone to vacuum leaks @ various locations. Also possible fuel injector problem as well. This test i am talking about can't be done at a parts store, a mechanic is what you really need to do the testing! You will save money in the long run by not doing unnecesssry work and parts swaping. Have the cooling system pressure tested for any leaks. If no external leaks can be found, suggest a combustion leak test to check for the presence of CO in cooling system as well = (Head gasket problem) mechanic will know.
Thanks for the speedy reply. Im not sure where the leak is coming from but I've been told I have a PO 401 EGR code and insufficient flow detected. Flow out of range. Also that the timing chain cover gasket needs replaced. I had 2-or three spark plugs and wires replaced last summer. So now the code reads 3 and 4 are misfiring. this is on a 2001 Ford Taurus 3.0L w/149663 mi
All wires and plugs should be replaced at tune up time as preventitive measure, EGR code you describe indicates that the EGR valve is either clogged or no longer funtioning you could try cleaning it out with carb cleaner and also check the pipes or passages going to it to see if they are not clogged as well, Finding out where the coolant leak is coming from is very important also...
do a visual inspection under the hood it could be something as simple as a leaky hose or fitting dripping on to your electrical system. make sure they are dry. find the leak and dry everything, and you may fix your misfire. Try that before you start throwing parts at it.