running hot idling high

[njschad]

i have a 1999 x 4x4 with 4.0 sohc auto trans... i bought it with 123,000 just rolled 143,000 yesterday then i started seeing some stuff late last night... when i start the vehicle the rpm's jump up past 2000 about to 23-2400 or so.. after a second or 2 it settles down between 1100 and 1500.. it only does this when the engine is warm... cold start is fine.. and at first this is the only thing i had noticed then i look down while driving on the highway and notice that the temp gauge is running high.. the temp gauge stays at least 3/4 the way to red and has gone a bit higher never made it into the red though... no dummy lights have come on, never had a CEL.. im pretty ignorant when it comes to troubleshooting a vehicle.. simple maintence and repair is no problem but i dont know what goes on under a hood with things like this.. any help would be great thank you all

 

[97greenmonster]

Id have your thermostat replaced and flush your coolant. About the idle, idk. Id start by checking all your sensors, MAF, IAC and what not. Give them a good cleaning with maf parts cleaner.