[Gaz64]

Peter,

You need to check for DTCs.

No doubt you have an APP (accelerator pedal position) or TAC (throttle actuator control) code set.

The throttle plate sits about 11% at key off. At engine start, the throttle will close to target engine speed depending on coolant temp etc.
The ECM pulls the throttle plate towards the closed position for idle speed control. It can pull the throttle even more closed to control road speed on decel when cruise control is used.