Lincoln mark viii turns over but wont start after sitting all night. Otherwise starts fine thru out the day. Seems like it started after changing spark plugs and wires

Are you getting spark to the plugs and normal fuel pressure ?

i would say bad fuel.....drain fuel add new...fuel filter may need changing as well

go out and sit in your car with the door open turn on the ignition key and when you turn it on you should hear the fuel pump prime in the gas tank, if you hear it prime up then its something else. If you don't its the pump.

test battery(amp load test) if ok, replace battery cables

is the security light flashing? its usually a problem with the security system. try locking and unlocking the doors with the electric locks and trying again. also if you have another key you might try that the ford house can check your keys are working properly

if you tried to jump the veh. when the batt. died, then you may have fried a fusable link in the harness. use a test lite to (CAREFULLY) look for voltage leading away from the batt. also you may want to check and see if someone can hear the relay click on as you try to start. (it is sometimes hard to hear it, so you want minimum back ground noise). good luck!

change the idle air control valve, this controls idling

Have you run a trouble code test, Kragen, Auto Zone and others do this for free, have the test done and post any codes here, I will try to figure out the problem based on these codes.

you need to replace your idle air control valve

ive tried turning the ignition on and off three times or so....then turning it off completetly for about five secs and then turning the ignition all the way on and most of the time it starts up....but sumtimes i think this car has a mind of its own......