We've got a John Deere X590 with under 200 hours on it and tonight when my wife went to start it again after just mowing the yard with it, when it started the engine was racing with the governor the only thing holding it back.  Tried it several times and it raced at full speed each time.  The throttle control (electronic) lever did nothing to slow it.  I took the throttle control lever out just to see if there was anything I could check on it (which I didn't take it apart) and tried the engine with no throttle lever hooked to it and the engine just ran kind of irregularly at a low speed and never speeded up.

I was guessing maybe  a bad throttle control lever -but they're close to $200 so I didn't want to just go buy one just to try.

  Anyone have any ideas what might be wrong with it?

TIA

Steve