Throttle body position - is this normal behaviour?

[FrankMcGar]

Hello,

'07 C70 here. Chasing down some issues relating to throttle body/idling. A curious thing I noticed when I was checking accelerator/throttle response with the engine off is that the throttle position takes a long time to snap back to the closed position. If I let my foot off the pedal it immediately drops to about 22% position, then after about 10 sec it goes back to the closed or starting position (which is about 17% ). This 10 sec delay is repeatable. I also have a spare throttle body b/c mechanic thought the issue was w/ the old throttle body, but they are both doing the exact same thing.

So I decided to hook up the spare one to the ecm and see if the physical response matched what I'm seeing on the scanner. Confirmed. Step off the pedal, throttle goes to 22% for 10 sec, then snaps closed. Is this normal?

[precisionguesswork]

If the car is running normal it's more than likely the ETB controlling idle air. It will stay open slightly etc. to control idle/rpms.

[precisionguesswork]

You can try cleaning it, but I highly doubt thats the issue since, as you said, it is repeatable with either ETB. (electronic throttle body)