99 F-150 Rough idling problem?

the truck has the Triton V8 in it its my fathers.It starts out when first started running rough,skipping etc when brake is pushed and in gear.It lurches and skips while in gear at low RPM's but after it gets warmed up and ran for a few minutes it will stop this and the whole time the Service engine light is on.Just trying to get an idea what it may be,gonna take it to autozone but I know some of these things dont show up on diagnostics.Thanks in advance.