my 240 is pissing me off.

ok so ive been trying to solve an idle problem. i used to have a fluctuating idle but i solved that with a new tps. now it just a high idle. i adjusted it to specs and it was runing at a normal idle. turn the car off and then back on and it shoots right back up to 1800-2000rpm. i checked my timing and thats ok. i tested my coolant temp sensor and its fine. i pulled codes from the ecu and i got a 55 so no problems that its detecting but there is obviously one present. now my speed sensor is totally out of wack since it says im going 90 km when idleing at 1800rpm. so we just disconnect that thinking it might do something and it was idling at 750rmp. turn it of and back on again. high idle at start up but thats normal then it drops back down to 750rpm. plug the speed sensor back in start it up and back to high idle. but what does the speed sensor have to do with your idle? its just there to tell you how fast your going.

anyone know why?