"I feel that there is not enough information to make a judgement. A shop has no right to do anything without authorization. Who was doing the authorizing? It sounds as though there could have been communications problems that kept the shop from pursuing more than had been authorized."
Steve, in my sister-in-law's shoes, I would have returned the car and complained. I don't know if she did, or if it was SO bad before that she was willing to accept any improvement.
I DO know the idle was poor by any benchmark as a result of a problem with the cable, and could not be missed by anyone who simply tried to start the car. Even when warm, it would be uneven and lumpy, as though misfiring, and when cold would barely stay running. Furthermore, I am a neophyte with these cars, and not a pro at all in this field - yet I diagnosed the problem easily.
My other comments relate to a quality of service and diagnosis I have come to expect from the techs in the shops I go to, and the way I have treated people over the years in my field. I just wonder whether others feel that a bit of pre-emptive diagnosis is or not what a shop should provide?