I have a 2000 Xterra V6. I drove it today with the usual no problems and idling at 800 or so RPM's while in neutral.
I did some unloading some old parts from inside the truck and went to move it out of the garage and this is where the problem started. I started the truck and it revved above 2500 RPM then the engine started loaping from 1800 RPM's to 2500 RPM's. As I waited the RPM came down a little but would not idle down from 1600 RPM's. No check engine lights or such and the engine was warm all along.

I reset the computer and still have no check engine lights or such. Drove the truck back home 20 miles or so and still the idel is at 1600 RPM's and will loap when you hit the gas for the first 5 seconds or so and stabilizes at 1600 RPM's.

Any ideas? It seems as if whatever tells the truck
that the engine is cold has failed?

Start by inspecting all vacuum lines to make sure they are not clogged, cracked, or have come loose. And clean down the throttle linkage by the air plenum. Maybe something simple as this.

Good idea. I'll try that first.

I was able to borrow an OBD2 reader. I got a code P0325, which the book says knock sensor malfunction.
I reset the computer with the reader and rescanned the computer, then started the truck and revved it some. I did this 3 seperate times and erasing this code. The idle seems to be staying at 1400 RPM's right now. All 3 times I reset the computer the same code kept coming back. I still have not seen the check engine light come on to tell me that there is a problem.

What happens when the knock sensor go's bad? This my problem?

I think you might have 2 seperate problems now. In your 1st post you said no check MIL's but that you had a high idle. The knock sensor isn't easy to get to. Do a search in this forum and I think I remember a posting that had photos of it's location.

Would a bad knock sensor give me high idle?

Finally got a day off work and had a chance to get under the hood. I found the clip that attaches the cruise control wire to the cruise actuator had come out. This was extending the cruise wire in length and holding the throttle partially open. Pushed it back in, problem solved.

Thanks for the tips. Also did the sea foam thing today.

Do you still have the MIL for the knock sensor?

I haven't re-checked yet. Although I took it for a drive after the fix and sea foam and it seems to be back to where it was. I will re-scan it tomorrow, if its still toast i'm gonna wait to buy the knock sensor as it's over $130USD from the dealer and $120USD from aftermarket. What does MIL stand for? Understood its the check engine light?

THE LIGHT WILL NOT TRIP FOR A KNOCK SENSOR CODE ALONE! You can see the code with the scanner, but there must be another code present for the light to trip.

Good to know. Is there going to be damage caused to the engine if I do not replace the knock sensor soon? The truck seems to be running great.

Unless you have a supercharger, I wouldn't worry about the knock sensor. It's located under the intake and is a real bitch to replace.