My truck's idle speed is high. I don't have a tach so I'll take a guess that the RPM's are roughly 3000. I unplugged the idle air bypass valve solenoid and idle speed drops to around 600. The problem was not fixed by substitution of the idle air bypass valve.

Help will be greatly appreciated.

Have a great day

 

Very strange indeed, I would have put money on the IAC after you disconnected it and the Idle speed dropped. So I wonder if you have a single injector throttle body? Take a look around that air intake valve (Not sure if they still call it a Butterfly) and see if it is not stuck closed or partially inoperative..etc.....

In the mean time if disconnecting it gets you 600 RPM, maybe you can run that way until you get it figured out.

Time to break out the Carb/Injector spray and really clean things up around your Throttle Body assy.