I have owned this DOHC Taurus for about three weeks. I bought it from an Estate sale. No warranty. No history. No former owner for that matter. I have driven it about 650 miles.
At first it ran very roughly, and at high idle. Scan codes indicated a miss on #3, and multiple misfires on first 1000 RPM on start-up. It doesn’t seem to be using any coolant, so I DO NOT suspect a bad head gasket or cracked head. I changed all six plugs and checked the resistance of the plug wires. Plug #3 was definitely bad. The intake manifold gaskets were replaced at that time. It still has the high idle, 2000 to 2500 RPM. I need to put it in neutral when coming to a stop, if I want to stop easily. Sometimes, the idle will slow to 1000 RPM at which time it will run roughly. Stepping on the gas brings it back up to 2000+ where it stays until its mood changes again.
I have looked for other vacuum leaks, pulled and pushed on hoses, shot carb cleaner around the new manifold gaskets, and swapped out the Idle Air Control with an unknown (hopefully good) one borrowed from my favorite friendly salvage yard.
Here are some questions Should an IAC be open with no current fed to it? I can see light coming through to the other side of my unit as well as the borrowed one. With 12V applied to the electro-magnet, how far should the plunger move? I think it should move towards more open. ??
Any other ideas?