I have a 92 5.8, this past week ive been having a problem when I turn the truck on it stays in a high idle. This doesnt happen all the time just when ever it feels like. It might been fine one minute then kicks right back into high idel while driving or parked. Ive heard this can be a common problem. Ive tried unplugging the bypass sensor and it idles right down or it shuts off, could this sensor be the problem or should I look to something else? Please Help

 

I think you mean the IAC valve, if you unplug it and it dies the IAC would be good.
Need more information:
Does your fuel pump run for one second when you turn on the key and not cranking?
Have you checked for codes?
Does your MIL (CEL) flash?
You might want check all of your vacuum hoses for an off and on leak.

 

Check engine light does come on. I checked the tps for voltage and resistance but I cant get a voltage reading for my low idle because the truck wont come down. the resistance reading was within spec the voltage reading was 5v with key on then running was 5v still with no change when the throttle was opened. Also just had it on the code reader and it said that the EGR wasnt opening but I cant see it being a problem with the idle. the coast clutch solenoid also came up on the code reader. Ive looked all over for vacuum leaks as well i coundt find anything. I took the Throttle body off as well and ther was some engine oil in there where would I be getting to excess crank case pressure from?

 

Bad PCV valve?

How about the fuel pumps, do they run for one second and stop or keep running when you turn on the key without starting it?