Originally Posted by bobko
Could be a vacuum leak. If you can, try to listen under the hood while the engine is running -- a vacuum leak can often be heard as a loud hissing noise. An engine with a vacuum leak (cracked rubber hose, usually) will show exactly the symptoms you describe: smooth and normal at high revs, but stumbles and dies at idle.
You could also check the idle air control valve (IACV or IAV, depending on who you talk to). However, a vacuum leak is the first thing I'd look for and it's easy/cheap to fix.
Thanks--there *is* a hiss... Are there hoses that aren't in plain sight to check? I sprayed carb cleaner on the ones I could see, but they seemed okay.