After changing my oil and filter, the throttle started sticking. The cable is free, but the linkage does not return on its own. I can manually push the spring to return it to idle. I've sprayed WD-40 and worked it back and forth to no avail.

Since this occurred immediately after changing the oil and filter I must have knocked something loose, possibly with the filter wrench. Does this little screw and spring on the firewall side of the linkage look ok? Any ideas? Thanks.

 

You have found the problem already. The little screw that has the spring under the head.... The tip of that screw should be against the tip of the "piston" that it's currently stuck against the side of.

 

You can see the two parts in the lower left image: thermowax and fast idle cam.
See if you can re-position the fast idle cam adjustment screw back onto the tip of the thermowax piston. It looks like it has been bent up a bit. Hopefully if you get it back in place the throttle won't bind anymore. But you will have to check operation of the fast idle cam as the car warms up because the cam arm being bent up is probably going to throw it out of adjustment.

 

Thanks, I evidently bent it while loosening the oil filter. I bent it back so the end of the screw is resting on the bottom of the piston. It seems ok now, at least it's not trying to rev to 7000 rpm anymore.

Would I need to readjust anything if the idle seems to be working? The check engine light came on which may or may not be related. I will drive around today and see what happens.

 

http://wright-here.net/files/manuals...sion_Cntrl.pdf

Check page F-82 in the link for the factory service manual. Shows how the cam operates, just make sure it's working still.
I think there is a document somewhere that outlines the adjustment procedure but I can't find it.