1981 Datsun 720 engine issue? Or what?

[Genwite]

Hey there. I just bought a 1981 Datsun 720 with the z22 engine and automatic trans. It's 2wd. I'm very happy with it and it runs great! So good in fact it doesn't like to shut off. I have no idea why but when I turn the key off sometimes it chugs as if it's running out of gas. Sometimes it won't do it, sometimes once, and sometimes it will keep chugging until I turn the key back to the on position and off again. I put a short video of it doing it once on YouTube. The link is below. I've tried searching this forum and others for help. I'm not very knowledgeable when it comes to engines. Any help would be greatly appreciated. It sounds like it's hurting the engine. But I honestly don't know. Thank you.

YouTube video is here:

http://www.youtube.com/watch?v=nZPSl65gtas

[sx moneypit]

Sounds like your base idle speed is too high.
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