I have 1998 crown vic and have had no problems at all except some coolant leak. I drove up the mountain today and car starting to misfire. It is cyl #4 misfiring (P0304). I am not a mechanic and don't want to pay for more than I have to in order to fix this problem. Any suggestions?

I have faced the same thing with my car, this is not a single answer to this problem. It could be a bad boot on the coil pack, it could be a improper coil install, sometimes the spring does not sit in well, it could be that the intake manifold is leaking, it could be that the egr valve is stuck, it could the exhaust manifold is leaking, sometimes these issues are not caught by the OBD 2 sensors, you can try to move the coils around to see if that works out.

air in the cooling system or coolant is low

you can drive it but it will damage your catalyst system, that is why the klight flashes to let you know other problems can develop. the car being a 2002 it has a misfire monitor in the computer. go to a local parts house and have them scan for misfire codes to see which cylinder is misfiring. make sure you check the intake at the #5 cylinder (which is the first one on the left side of the engine)to see if it is getting coolant in it from the intake leaking at the thermostat housing.

Change your coolant sensor

Do you have a check engine light on. With that mileage I would start with spark plugs. You might end up replacing a coil or two.

Now you go to a repair shop, and have it diagnosed

You have other codes for the coils,forget the PO300

You will need someone good with ford ignition issues,
to resolve the misfires, and possible do some other
preventative maintenance work,as the stalling is
another problem

Maybe, Ford motors are sensitive to airflow changes, a slow responding MAF can cause delayed signals to real world conditions. An UNDERreporting MAF will ENLEAN the fuel charge as delivered to the injectors. This can feel like or perceived to be a misfire/coil problem, BUT ONLY UNDER A LOAD. Check all PCM inputs, condition of components.What is more logical: EIGHT (8) coils OR EIGHT (8) injectors failing AT THE SAME TIME? I would look at a single component scenario insteadwise, fuel pump? ACT sensor? TPS? EGR solenoids? MAF?

ignition switch or starter relay or a wiring problem

your egr on that side is dirty try cleaning it aslo check intake boltsaround those clyinders.

I would try to replace your spark plugs, and spark plug wires, My 88 Vic did the same thing...now it runs like a champ....you could also try fuel injector cleaner.