i know this is a strange one and it freaked me out the other day. when going down the road i did a quick accel to 55, i let off and the blazer goes up to 60 on its own up a hill. i was no where near the gas pedal i checked all the mats, nothing was stuck so i sent it into neutral to stop it thinking oh my god this toyotas gonna kill me. the rpms went down and i slowed to a stop, i said hmmm drove home normal nothing happend on the way back but again i accel quickly to 60 and it stayed on till 65 any ideas what this crazy thing is doin

 

old throttle cable? something jamming it under the hood?

 

Had something similar happen on my Chevelle a few years ago. The air cleaner had come unscrewed and wasn't letting the throttle close all the way. Get under the hood and manipulate the throttle linkage, checking for any binding or sticking.

Also, just a thought, but if your Blazer has cruise control, maybe that is acting up. I know on my '95 there are two throttle cables, one is for cruise. Unhook that one, and see if your problem happens again.

 

Also check that the throttle blade isn't sticking in the throttle body. On my wife's 2000 Blazer the throttle body was all gunked up when we first bought it and I had to clean it up enough to get it to operate smoothly and not stick.