Idle often runs high

[BlueOvalBoys]

I have a 90 f250 with a 5.8L 5-speed transmission EFI cruise control 4X4. I am the second owner and have owned this truck for over five years and have never been able to diagnose the problem. engine starts and runs normal, however the idle 'sticks' when in nuetral, idles at roughly 1500-2200, when i quickly tap the gas the idle kicks down to a normal 750. any help at all is greatly appreciated. here are my father and I's ideas

1. Automatic choke might be sticking (it is injected so shouldnt have a choke though)
2. Throttle cable linkage may be hanging up, gunked up, or kinked (looks fine however)
3.Throttle body butterfly valve is dirty or damaged (i have cleaned and rebuilt it already)
4.General vacuum problems
5.the cruise control cable is faulty (recently the cruise control went out, the idle problem has been around from day one though)

 

[Crewcabber]

Go to a motorcycle shop and get some cable lube.
Pull cable off and lube cable.
Check and make sure the able isn't popping out or getting stuck.
Wd40 pedal pivot
Could be a sticking or bad tps.

 

[BlueOvalBoys]

Thanks

Have been super busy for the past few days, this weekend we will be doing a lot of much needed maintenance. I am going to get the cable lube tomorrow and will try everything you have suggested. To be clear what do you mean by the tps?

 

[SuperCab]

I think he's talking about the throttle position sensor

 

[dustybumpers]

Take the little plastic "hat" off the top of where the throttle cables hook up


use your hand, and open and close the throttle, watch the plastic piece at the end, and see if it is hanging up under the spring.

If it is, replace the cable

 

[oldbeater]

i had a high idle, and it turned out that the bolts on my lower intake were just sitting there loose. Three were tight; the rest were not even started.