Lets hope the OP hasn't done just that - the throttle valve minimum position stop screw should never be adjusted.Have you adjusted the idle screw under the hood?
Have you checked for obstructions? Someone put duct tape under mine to keep the idle up, worked good until engine got warm, tape got soft and then it idled like crap.
Is the battery good? (can cause all kinds of weird problems) holding a charge and outputting at correct voltage.
It sounds like a sticky Idle Air Control valve (IAC or ISC), and can often be cured by cleaning it with carb cleaner.Seems to idle fine until engine warmes up. Once temp is up the engine will stall when stopping or slow roll. Runs fine when at crusing speed...
How did you figure out "where you thought it should be" ?If someone who didnt know what they were doing adjusted it, it would be wrong to adjust it back?
Someone adjusted mine and had stuck duct tape under the cable. Car would run fine for a little bit than turned to crap. Putting the screw back where I thought it should be and removing duct tape fixed my issue.
Never adjust or not it fixed my problem. Why include it and make it adjustable if you should never adjust it? It gives a how to in my chiltons (or haynes) manual.
The Throttle Stop Sccrew is factory set and must not be adjusted. Any adjustment will negatively affect the engine performance.