It actually might have nothing to do with the sensor (and the sensor your thinking about is the MAP, which detects the load on the engine and tells the PCM to adjust everything accordingly.).
The most common cause of a low idle on older toyotas is the IAC (idle air control) solenoid. It can get gunked up with carbon over time. The IAC is what controls your idle, so if its not working right, your idle will be off.
It takes maybe a whole half hour to clean it out, so even if its not the cause, its not like you wasted your life.
I dont have a link, but there is a walk-through on how to clean it somehwere on the rav4world forums (
http://www.rav4world.com). you can look it up there.