Derrick

I have a 2000 F-150 with a 4.2 V-6 and it started to idle rough when it would start and then it would work itself out and idle fine after a few minutes. It does not do this every time after it starts just mainly after it has not ran for a while. The check engine light came on and the diagnostics test at auto zone said cylinder 1 and 3 misfire. Changed the plugs and wires and it still did it and test said the same thing was occuring. Then changed the ignition box that the wires plug into, thought that would for sure fix it but it still has been doing the same thing and the check engine light is back on. Any suggestions would help a lot. Thanks.