I replaced my throttle motor to see if that would eliminate a intermittent stumble. But with a new motor the engine starts, revs up high and then shuts down. I put my old motor back in and it does the same thing. So there must be something that needs to be set up or aligned when installing the throttle motor. Can anyone enlighten me?
Thank you.

 

There most certainly is some sort of alignment procedure for installing a new motor/tps sensor. My suggestion is to use a logger and see what the TPS says it is at rest and you'll probably get an idea of what you need to do pretty quickly. It's likely to involve turning the motor housing to a certain position before installing it and then lining up the bolt holes. I haven't looked this up and I don't work for Lexus so I could be very wrong.

 

You have to disconnect the battery and hold the cables together to reset the computer after changing things to do with the throttle. It was learned to the original one's position etc. You can find the adjustment procedure online in several sites. But first install the new one, set it with the DMM or feeler gauge method, then do the battery disconnect/computer reset. Then it will have a fighting change to work.