I've asked on the Taurus Club forum, they're clueless on this. Hoping there's a Ford expert here who knows what to do. My 1997 Taurus LX suddenly started to run horribly. 108K miles. Definitely time for new plugs and wires. The IAC passage in the throttle body was almost totally choked off. So I cleaned the intake, the throttle body. Installed a new genuine Motorcraft PCV valve and new rubber hoses for the PCV. After all that, it would not idle below 1,000 RPM under any conditions, usually wanted to run a minimum of ~1,300 - 1,400 but some of the time it'd go up to 2,000. I replaced the TPS and IAC. Made it a little better. The original IAC was extremely crudded up. After a lot of searching I found how to reprogram the WARM idle. Run the engine up to operating temperature then shut it off. Restart and let it run for a full two minutes in each of these conditions, without allowing the car to move. In park with AC on. In park with AC off. In neutral with AC on. In neutral with AC off. Foot on brake when in neutral. Those can be done in any order. After doing that, it will idle normally once the coolant gauge comes off the bottom. But until then it will run the RPMs up and the crazy thing can hit 30 MPH with my foot off the gas. Since it will run correctly once it's warmed up, it can't be a vacuum leak. It must be opening the IAC to 100%, had to have been doing that before I got the warm idle set. Apparently it adjusted over time as the IAC passage progressively clogged, and still has bad data stuck in there for cold idle.