Ok here we go, i hope include all pertinant info but if i leave something out let me know. last week i noticed my gas mileage was less than usual by 40-50 miles per tank, i know my check engine light is out and i havent bothered to replace so i hooked up my scan tool (innova 3100a) to see if it would reveal the casue, i had only 1 dtc which was p0303 # 3 cylinder misfire. i have also notice that my rpm's are about 200-250 higher than normal, im sure this is the culprit to bad gas mileage, the only question is why. my temp gauge on the dash reads ~165-170, where it alwas has since i picked it up back in january. i havent done anything to repair the # 3 miss yet, not a top priority it just idlse a little rough but cruises good other than rpm above normal. freeze fram data at time of dtc shows that fuel sys # 1 and 2 are closed, calc load is 18%, coolant temp 192, stft bank 1 and 2 1.56 ltft 3.53,MAP was at 16.85 in hg, MAF was 4.57 lb/min, engine rpm 2114 and speed 60. my first thought was i was running in open loop but scanner says otherwise. i have checked again and again for lose wires and vacuum lines and cant find any, could my miss fire be causing the higher rpm or is that a separate issue. i have no other codes showing. any ideas ould be greatly appreciated. when i first start driving when its gets warm it will run normal rpm, but after accelerating back to speed it will not return to normal rpm's. ok i think i have discovered that a check engine light causes the engine to go to open mode, can anybody verify this.