ok I have come across a issue in my truck I have never had or seen I put my truck in park today after driving for about 2 hours and the rpms slowly start to go up on its own it stopped at 2200 rpm I turned it off and restarted it it idled normal shut it off again to go into the store restated the truck after about 10 minutes and it idles high again stopped at 2200 again then came down to 1900 I looked under the hood to see if anything was sticking didn't see anything out of the ordinary put it in gear it drops down to normal it didn't slam into gear was nice and smooth drove 20 minutes to home and put it park again didn't idle up stay normal had no codes or anything drove fine any ideas were to start looking

 

Could we ask you to post some info?
What is the year, motor and trans?
The running account is not much help with no info.
We understand the idle is intermittent. That's about all.
What did you expect you might see by lifting the hood?
Good luck.

 

Its a 99 f150 half ton with a 5.4 I don't remember what trans I was looking to see if anything was stuck causing the high idle

 

I think he wants to know if it's an auto or standard.

 

Ok, now we know it's an F150 with a 5.4 motor and auto transmission.
Idle:
Idle is controlled by an active air bypass called a IAC.
This often gets gummed up internally. You will never be able to see this from outside just looking at it even if you knew where to look under' the cover.
.
Next is the throttle body bore. Same deal.
These items need to be opened up/ taken off to clean them up and check for manual operation.
.
IAC is held on by two bolts and Electrical plug.
.
Throttle body can be accessed by removing the big air tube. In that large bore you see the round plate that opens with throttle operation. Around it often collects dirt and gum.
.
Get a can of spray cleaner from the auto store to clean both these parts until they come clean.
Check the Pintel for free sliding operation inside the IAC.
Reinstall and see if it solves the erratic idle issue.
Open the throttle plate by operating the outside lever. Spray around the bore until is comes out clean.
Reassemble all parts as you found them is a must.
.
Operation:
Idle is controlled solely by the computer as long as there is no mechanical/contamination interference. This is how cold start high idle and control is accomplished by inputs from several sensors to calculate the idle and fuel control signals to the IAC and injection.
If you find the issue is still present, we know what it is not and can proceed to look further.
Sorry if I pushed a bit but you were not realizing what you were getting into to and it takes some work to accomplish on a 15 year old vehicle.
Good luck.