stalls when idling warm

[mannsjp]

I've a 96 SW1 w/151K. Mileage about 30mpg with ski box on top - about 35 without. Most stuff original under the hood except usual - (ECTS, serpentine belt, etc)

A few months ago the car started to stall idling when warm. Cold idle is fine - sits around 1100rpm until it warms up. After it's warm is when the problems start. When you pull up to a stop light it will idle happily at 800rpm or so for 10-20 seconds before it starts 'hunting' - going from 500 to 1000+ rpm every 2-3 seconds until it finally dies.

If you turn on the A/C, the problem goes away, but of course the idle gets bumped up to 1100 or so.

Finally had time to look it over this weekend and try many of the very useful suggestions that have been posted related to idle issues. I've tried the following:

-Verified ECTS was the brass one. No apparent corrosion on connector. Temperature indicates normal when hot. (hair over 3/8 full scale)
-O2 sensor replaced awhile back on unrelated issue
-Removed throttle body & cleaned up all the small ports, especially where the IACV pintle mates up to the housing (it wasn't too bad to start with)
-Checked for vacuum leaks with starting fluid
-Replaced TPS with new one.
-Replaced IACV with new one.
-Reset the computer by pulling the negative off the battery after replacing IACV & TPS
-Covered EGR valve ports with 'pop can' and test-drove - still stalled at idle
-Replaced plugs & wires (they appeared original) (Running out of ideas...)

When I cleaned the throttle body, I did notice the throttle stop wasn't touching the end of the screw - i.e. the throttle closed all the way. When I replaced the throttle body, I turned the screw in until the idle went way up to 1500 or so, then backed it off 'till the IACV took control of the idle.

I looked at the plugs after it had been idling for 1/2 hour or so and they were pretty sooty. Yet they looked pretty normal after the trip back from the parts store to get new plugs. I don't know if this is normal or not.

The SES light had been on occasionally before this weekend. I haven't fetched the codes out of it yet, but the SES light has been off since I got done goofing around with it this afternoon.

What did I miss?

[fdryer]

Well, there's not much left to replace with 150k miles on this engine except for a new thermostat and map sensor.

Try this next time when the engine's idling as soon as possible before it dies; have the air intake off to expose the throttle opening and tape over the hole in front of the throttle plate. The idle is supposed to drop down to 500-600rpm so readjust the throttle stop screw where its supposed to idle from factory specs. See if this clears up the uneven idle when removing the tape.

[mannsjp]

OK I'm stumped. I thoroughly cleaned the throttle body, then adjusted the idle screw so it idles about 600 rpm with my thumb over the idle air port. Not an easy thing to do, as even with my thumb over the port, it still hunts some. Maybe falters and recovers is a better description.

Replaced the MAP sensor, as there really wasn't anything left to do I could think of. That didn't help either. Also disconnected the battery thinking a system reset might help - no luck.

[fdryer]

Vacuum leak, thermostat, and catalytic converter left. Try spraying around the intake manifold with water while the engine's running. Loose throttle body?