89 Ford 351 Very High Idle

Vehicle overheated. It was a blown heater control valve. Right before pulling off, the engine shuddered, and the idle jumped to a very high idle. Replaced the HCV, no cooling issues.
Now it cranks up normally, and about 10 sec later revs up to a very high idle. No mechanical obstruction with the throttle.
Stalls when you try to move it. At idle very high rpm.
Any ideas.
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Fuel system type? EFI, CFI, Carb.. WHAT!????
Start by disconnecting all vacuum access, lines and plug the port. If it has EFI, leave Fuel PRess Reg connected.
Check PCV valve
If still goes high idle, disc wiring connector for Idle Speed control.
On overheat, though might point to bad intake gasket, can be
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