A few weeks ago after a very bad day of rain and going through a lot of big puddles my truck idles strange now. When its cold it will idle around 1000, which is normal but will sometimes jump as high as 1600 RPM's. When it is at running temp it will jump even worse, idling around 650 RPM's jumping anywhere from 1500 back down to 650. It only does this in park and neutral though. Any ideas?

 

Possibly TPS. Wouldn't hurt to test it.