140,000 miles and never an engine problem, Then yesterday stopped for fuel (had just come downhiil from 8500' to 5000'). Starting up, starter turned for about 10-12 seconds, then fired but would not idle--rpm went to about 500 but died quickly. This happened 3 times and on the 3rd start I pumped the accelerator slightly and was able to keep the engine running, but then it slowly (with no pressure on the accelerator pedal) increased to 3000 rpm and remained there. I had to shut it down because I did not want to put it in gear at that idle speed. I repeated this process again (difficult to start then the over rev), and shut it down. The next time I started it it it did not overrev and I was able to continue to my destination. Now it starts, but needs accelerator input to initially keep running, then will roughly idle at about 600 rpm.
Additionally (coincidentally?), yesterday and today, after shudown the engine fan runs for several minutes. The temp gauge never was over half scale. This also has never previously happened.

Ideas?