1) I will be washing the car if you visit me at 5 tomorrow.
2) I have been washing the car since 10 am."
3) I had been washing the car when my friend visited me.
4) I will have been washing the car for hours when you visit me.
Yes, you have an agent "I" and a direct object "car" in all four. So passive is possible. The results of transforming these into the passive voice are, however, infelicitous, not to say 'stinkers'.
1) The car will be being washed by me if you visit me at 5 tomorrow.
2) The car has been being washed by me since 10 am.
3) The car had been being washed by me when my friend visited me.
4) The car will have been being washed by me for hours when you visit me.
("you visit me" in these can also by passivized as "I am visited by you".)
P.S. Your remarks on "while" / "when" touch on a subtle point. Still, the keeping silent and the talking are happening (if the command is obeyed) at the same time.