Hi there, I have a 99 XLT V-6, cel came on and read a missfire on 4th cly, I replaced the plugs and wires to no avail,(plugs all looked fine)and for the heck of it replaced the fuel fiter, any ideas what I could try next? Am I right in assuming the 4th cly is the front drivers side? Thanks for any ideas you can give!!

 

Could be a bad coil pack. Check to ensure that the coil connectors are clean and remove coil pack, clean the grounding surface and reinstall the coil pack to see if it clears the problem. If not, I would lean towards a bad coil pack.