Too fast idle

Hi all. Have a 93 DD 3.9l. It idels too high 1000rpm's at park and warmup. Have replaced plugs wires pcv..How do i adjust this Fast idle cam to lower the idle RPM?. If im NOT supposed to do that what do I do?

Thanks

A slightly higher idle speed is normal after a cold start...1000 to 1200 rpms is the typical range. Once the ECM senses a rising engine temperature, it will gradually reduce throttle to normal idle speed.

If the truck is ALWAYS starting up idling high regardless of temperature then I would check your engine temp sensor.