I have made a few comments about the 1980 300SD that my cousin gave me after going into runaway. His wife had started the car, and it immediately went into runaway. It was revving at full bore, and required the fire department to cover the turbo intake. She said it was the loudest and scariest thing she had seen. When it was GLADLY given to me, all evidence pointed to a stuck fuel rail. I swapped out the IP (obtained from Craigs List for $120), and got it to run fine. I then returned the car, and explained that the problem is fixed, and that she would most likely drive it for another 200,000 miles without ever having the problem again. She looked at me incredulously, as though I had a hole in my head, and said "that car is possessed, and I don't even want you to drive it". I enjoy driving it, no sound better than the 617.95X idling, except perhaps when it is revving at 5,000 RPM.
Will

I just found this video of a Land Rover Defender turbodiesel running away:
http://www.youtube.com/user/Rick0rz#p/u/7/5zx3qKX_Pno

With an engine revving that high and smoke coming out like that, there's no way I would want to get my face anywhere near the engine, let alone start trying to disconnect the intake so I could block the air intake. I think I'd only attempt that if the intake was already off and I had just started the engine after repairs.

It doesn't sound like all 'runaways' are this dramatic but as much as I would want to save an engine in a nice car such as a Mercedes or Land Rover, I would be afraid something could let go - like a belt fly off or even a rod get thrown right when I was standing over it....would rather lose an engine than my face.

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1976 240D "Katja"