As mentioned, the idle is fixed by the computer and can't be adjusted without doing more work than you need to. Here's what I'd do:
Check adjustment on the TPS - voltage at idle. Terminals have probably been covered here, please let me know if they have not. Output voltage (Key ON) should be 17% of input voltage - whatever the input voltage happens to be.
If that's good, remove the throttle body (get a new gasket,) and disassemble and clean everything but the TPS! Do not get water on the TPS - electrical contact cleaner works neatly, you can use an old toothbrush for the really nasty bits.
Those are the two big ones. Let's see, what else would I look for (in no particular order):
- Vacuum leak.
- The MAP line often comes loose from the passenger side of the throttle body. Pop it back in.
- Check for "carbon tracking" under and along the outside of the distributor cap - it literlally looks like someone drew it on with a pencil. Replace the cap if present.
- Check resistance on your wires, make sure none are "over spec" or "under spec." (I'd have to look up the actual range of values you're looking for.)
- Check to make sure your spark plugs are clen and tight. It's rare, but I've seen spark plugs work loose (usually due to improper installation.)
- Check to make sure the terminal in teh HT lead makes good contact with the button on top of the thing.
That's most of the causes - let me know if none of them pan out for you.