Tune ups plugs wirers

Look under the hood to see some bare cables that connect the throttle pedal to the throttle body. Turn the idle screw clockwise 1/2 revolution at a time. Start the car, let it warm up and try it. Make sure the rpms aren't above 750 RPM or you'll risk crashing into someone. All this is assuming the car is in good tune, running well, has no major issues etc. These cars were pretty cheap and cheaply made so you may be limited by the age and lack of durability

if you replaced your spark plugs and wiring check to make sure your wirers are in the correct firing order

My first suggestion is a tune up. You would be amazed at the difference new spark plugs and wires do for a missfiring engine.

part store can tell you that bud 40or 50 for wirers about 20 for plug high end for plugs can get for around 1 each

If you bought the spark plugs at auto zone,these are factory seconds,and will fail under the ignition system you have,check the coil boots also,make sure they are good and the boots are on good,but it is most likely in the ignition area.

Several engine sizes there...

1999 Ford Expedition 4.6 liter SOHC V-8 VIN "6"





1999 Ford Expedition 4.6 liter SOHC V-8 VIN "W"





1999 Ford Expedition 5.4 liter SOHC V-8 VIN "L"




Hope this help to solve it (remmeber comment and rated this).

http://autorepair.about.com/library/firing_orders/bl-fo-14344.htm

Try this web site for the info.
I hope this works!
Good Luck .!

engine misfire. a tune up plugs and wirers should fix your problem (use ony ac delco spark plugs)

check or replace plug wirers. could be the coil pack .located @ other end of plug wirer

If you remove the engine cover from inside the vehicle you will gain access to the spark plug wires and spark plugs. The spark plug wires come out of the distrubtor cap thats at the rear of the motor, the spark plug wires run to the left side of the motor and to the right side an end up attached to the spark plugs. Reolace spark plug wires one at a time so you dont mix them up, this is fairly easy the only difficult part is getting your hands in the small space in the engine compartment. Hope this was helpful.