truck is ideling i would guess around 1500 to 1800 maybe higher at times and i have done everything that i know to get the idle down with no results. soon as truck fires up its instant high idle cold or hot . i have checked for vaccum leaks by spraying starting fluid over the whole motor seeing if it would make it idle up or down i know this is not the best way but it works, i put a new tps on it. cleaned the iac, unhooked the neg battery cable to reset the computer still nothing idles smooth as silk but very high took the idle screw all the way out and the throttle body flaps are completly closed. cable is working proper whats going on guys help please

 

That is the key right there. That means you are getting unmetered air aka vacuum leak into the intake. Do not forget your truck has more than one metal vacuum reservoir that are known to rust through and leak. That is why I do not trust the "spray carb. cleaner" around the engine method. I use a hand held vacuum pump/gauge to test each vacuum circuit.

You really should not have messed with the throttle stop screw, but at least you now know it is not the cause of your high idle.

 

To rule out the IAC completely unplug the connector while the engine is running. If the RPMs dive down and the engine stumbles or barely runs, then you know the IAC is good and you have a leak elsewhere.

If the idle doesn't dive down, then the IAC is stuck open. This happened to me recently... all of a sudden my idle shot up to 1800 RPM and refused to come down. I unplugged the IAC, noting happened, I replaced it, and all was good from that point forward.

 

It always pays to have another set of eyes look at the problem!

 

I had a 1991 f-250 that ran like a swiss watch....as i was pulling out my bro from the ditch one night the idle shot up to 2200 rpms.....i replaced the IAC and it fixed it....

 

well im pretty good under a hood of a ford i was just asking on here to try to save some time .i know spraying starting fluid under the hood of a running truck isnt the smartest thing but it helped me find that the upper intake gasket was leaking (cause the truck to stumble terrible) i replaced that gasket and it brought the ideling down some but it was still high next i checked the iac and it was bad so i had several of them laying around i changed it and it idles around 600 rpm now .

 

Thanks for the feedback, glad you found it!