I am having the exact same problem now with my 1992 4Runner - 135K Miles (when I first start it in the morning it works fine. After a 30 minutes of driving I stop the engine. After I come back (20 min later) I restart the engine. The engine idles very rough. It seems like it wants to die. It idles just above the 500rmp marker.)
Did you ever determine the real problem? and how to fix it? Thanks -
4RunnerTampa