Ford Repair: 1987- 302 V8, ford dealers, crown victoria

Question
Crown Victoria 1987 302.
After driving it for some time the idle goes to
1400 RPM. Replaced:thermostat, coolant sensor,
idle solenoid, egr, manifold air temperature.
If you turn the engine off and on again it goes
back to normal.
Thanks, Jack

Answer
Jack, the problem you describe needs some diagnosis by a technician with a scan tool.  Most Ford dealers don't have the old EEC3 scan tools anymore, but if you know a shop that's been around a long time, you may find one.
The items I would look for include testing the MAP sensor and TP sensor, and perhaps swapping the PCM for a known good one.  
You might also want to clean the throttle body with a good carb cleaner - if there is some carbon holding the throttle open, or if the TP sensor is mis-adjusted, that will cause the PCM to do crazy things with the idle.
Hope this helps...
Clay