Throttle Sometimes Sticks

I have never heard of a throttle position sensor causing this, but there is always a first time. For a mechanic, the goal is to get it to stick and stay that way long enough that we can find what is causing it. What I would do the next time this occurs is to stop the engine, then carefully remove the TPS. If the throttle blade snaps closed you found the suspect.

If the throttle blade shaft is sticking, you would have solved that with the new throttle body, but more importantly, the shaft and / or bushing would be ground up making them rough, and that would cause a major vacuum leak that would result in a too-high idle speed all the time, including after you force the throttle blade closed.

What I have run into is with throttle bodies that use a quarter-round cable guide, the cable from the cruise control servo can fall off to one side, then it is not long enough to let the throttle close all the way. There is always an underlying cause for that like a kink in the end of the cable or the mounting bracket is bent or miss-positioned. You would have seen that by now.

I've had carburetors that did this when the throttle shafts got chewed up and became rough. The force of the air blowing against them would cause them to bind, but once they were stuck, they would stay that way after the engine was stopped. The additional clue was sometimes you'd feel them stick, then suddenly pop free when pushing on the accelerator pedal. One got so bad that at times you couldn't even push the pedal. You had to release it, then push it again. Other than the misery of the sticking, those didn't really cause a high idle speed because little air was sneaking in through the shaft and bushings. The fix for those was to just install a good used carburetor. They were so cheap and we all had extras laying around, so it didn't pay to try to fix one. That problem wasn't common either, so it was not likely the next one would do the same thing.

When this happens to a throttle body assembly, the resulting vacuum leak typically leads to a high idle, but I've never run into one that caused sticking. To have two do the same thing really surprises me. I'm still leaning toward the throttle position sensor. Cleaning it isn't going to do anything if there is some mechanical issue inside it. Unbolt it from the throttle body, then see if the sticking still occurs. Those sensors are sealed so you're not going to get any cleaning chemical inside it and onto the sliding contact. I used to take a lot of them apart and connect hidden wires that ran to switches to make "bugged" cars for my students to diagnose. Due to their internal construction, I can see where a mechanical problem could develop, but that would be pretty unusual.

I'm just about out of answers. The only other thing I can suggest is to look for external linkages or controls that could be causing this. I looked at a photo of your throttle body and throttle position sensor, but from those I can't see any obvious suspects. I also looked at the idle air control valve. That is the same design that Chrysler and GM used for many years. It causes very few problems. Even if that wasn't working properly, you wouldn't see anything snapping free like you described.