I was doing some stop and go driving and all of a sudden my s-10 blazer started to idle at 35mph and would not come back down. No codes are being thrown and I dove it in the around but nothing, I don't see any kinks in the throttle cables and the throttle does not seem to be stuck in the open position.

Any thoughts?

 

A large vacuum leak or a failed IAC valve could cause this in addition to what you have already checked.

 

Mine does the same thing every now and then. It also spikes to about 2.5k RPM on startup about half the time too. Recent changes included a IAC Valve, and the TPS. It started randomly one day, and if I let the engine warm before driving it, the problem goes away. Seems to be worse on cold days, which probably means a cracked vacuum hose that seals itself when it warms up. But who knows... its not a big problem, but when it does this, your brakes will wear faster.