I have an 01 windstar with misfire on cyl 3 and 4

Plug wires

Believe it or not the firing order is 1-2-3-4-5-6 The cylinder locations are 2-4-6 in front by radiator, and 1-3-5 against the firewall. If you have a misfire on a certain cyl. and you've replaced the plugs,wires and cap and rotor, you probably have a fuel injector that's dead or plugged,it's common on Quests. Figure out which cyl. is misfiring and unplug the fuel inj. conn. with the engine running and listen for a change in RPMs. If there is no change then replace the injector.

misfire on cyl no 1 on a 01 merc grand marq

the misfire could be the distrubiter cap also could be bad...tha cap is where the other ends of the spark plug wire go

What is the code you are getting? Have you checked the engines compression and all cylinders are in good shape? Do that test and get back to me.

replace coil pack

change all plugs and the egr valve.

Coil pack and new plugs and wires would be my advice .I have a 2001 windstar and that what mine was doing and coil pack and plugs and wires fixed mine

#1 is the egr position sensor #4 Is for single cylinder misfire so this could be the coil or a bad plug or wire ..but with fords should check for a vacume leak that can cause a misfire to .....#2#3 are 02 sensors before i would change them i would check the mass air flow sensor ..Hope this helps

Hook up a vacuum gauge .
Vacuum test 01