My '94 Suburban won't idle down sometimes. Did it 2 months ago so I changed the TPS and it seemed to work. Since then I have replaced the fuel pump (it died on me) and filter, towed a 5000 lb. vehicle for 200 miles and not a problem. Today, while climbing a small hill, the rpm's wouldn't come down. After I shut it down and left it sit a while, I started it and everything was normal till I started driving and it stuck again. Shut it down again and let it sit awhile and it's fine again. Any suggestions? Thanks