my truck has always idled like crap i have replaced the tps and cleaned the iac and cleaned the tb the best i can without taking it off i dont see any disconnected vacuum lines. and today it was running fine but when i got home and put my truck in park the rpms shot up to 1500 rpm and sat there until i hit the gas and then it dropped back to normal so i backed up and tried it again and it did it again and after about a minute it dropped back down on its own?? any ideas. 02 ram 2500 4x4 5.9ltr

 

idle speed (slow - med - fast) is controlled by the iac. nothing more, nothing less. if your idle speed isn't right, i'd recommend replacing the iac. its about $40-45. cleaning it is sort of if'y. i'd also recommend removing the TB to clean out the iac plunger well and contact point of the plates.