Truck stuck on idle

A serious answer then. There is no semi truck out there that will get past 10,000 rpm. That's not your problem.

So the question becomes just what are the symptoms? What have you done so far for diagnosis?

You might need to get it towed to a dealership so they can hook the computer up to it

 

Probably a bad "knock sensor". JMO

 

No, you did not.
And again, if the mechanic cannot diagnosis the issue you need to get it to one that can.

 

It's directly behind brake pedal, on a wall behind plastic wall cover. Sorry that all I know

 

Can you idle it up higher on the cruise/ high idle switch ... if so it may be your throttle pedal switch .. the hissing sound should be easy for your mechanic to find if he can’t maybe it’s easier to find a new mechanic

 

when you correct him and said said 1000, he did correct you again to tell you 10k rpm
very confusing fellow