I don't care whether or not you think it would make sense for there to be a switch, that doesn't actually have much bearing on whether or not there is a switch.sliverstorm said:Figures. Why would it be right-side up, that would make things too easy. Though it still looks to me like there is no *switch*- which really makes a lot of sense to me. The simpler it is, the better; esp. when it will move a bajillion times during it's life. Just think of how many times you've moved your gas pedal.
There is a diagram at the top of FI-58 that clearly shows a switch between E2 and IDL. The chart that you showed, clearly shows that the resistance between IDL and E2 changes drastically from < 2k ohms to open circuit over a very very narrow amount of movement. How could that be anything other than a switch?
But you want a reason why there'd be a switch? The TPS isn't very accurate, and it serves multiple purposes. One thing that it does is tell the computer that the throttle position has quickly changed. The airflow meter isn't really fast enough to keep up with fast transients, so a good approximation from the TPS is helpful. If you are cruising with constant speed, the TPS is next to worthless between the AFM and the O2 sensor.
The TPS is also used to inform the computer if its at WOT or idle. It needs to know idle very accurately because it has to do a host of things to keep the car idling properly when your foot isn't on the throttle so it has to be very accurate. The potentiometer just isn't that great for that purpose, especially when its near one end. On otherhand, WOT isn't as critical, since WOT only really engages the extra-enrichment, and does it really matter if that enrichment comes in at 90% WOT or 100%? Not really.