Hi i have 1990 miata yesterday this happened

 Hi  i live in massachusettes so the weather is a bit cold out.  The miata has started to idle fast., i looked at the trottle and sprayed but it is not sticking. I known it isn`t the cold weather either because it won`t trottle down even after 1/2 hour of running . Some one suggested try fuel injector cleaner. I will try that, but does anyone have any other ideas what would cause this fast idle to happen.
 
thanks to all !!!

I've never seen what's under the hood of your car, but you must have an idle control valve or something that translates engine temp into an adjustment in your idle.  Check all of your vacuum lines for leaks first.  Your idle control valve may be tring to compensate for something (like the AC on) by sensing a change in vacuum pressure.  Make sure all your temp sensors are tight.  Start simple first. 
 
I'm an ex Saab mechanic, so I'm just trying to apply what I know from that. 

 Thankyou for the tip. I will look for loose vacum  line also.
 
 thnks again,

also, my dad had a similar problem with his truck. with his it turned out that he got a replacement thermostat that allowed the engine to run a few degrees warmer than the stock specs and his truck would never get to the right temperature for the idle to drop. this may not be the case here though because i hear that this occurance is rare, but if nothing else helps, consider that.

Try this: run your car w/out the a/c on, then try it with it on.  If the idle gets higher with the a/c on, the idle air control valve is overcompensating.