I have had both 1kohm resistors and potentiometers go bad. I have had a pot in for quite a few years and I'm on my third one. The first two were cheapo's, the last is a 5 turn 5kohm from Mcmaster which has been good for several years now. I have a digital voltage gage to monitor the tps circuit also. But I had the same symptoms you're having when the first two pots went bad.