With 36 views in a couple of days, this idler pulley doesn't seem to be a common failure. I have ordered an AC Delco part of Amazon to replace the AZ Duralast that I installed a year ago. I will keep the used part in the trunk, just in case.
With over 160k miles and relatively few problems, this Milan has been an inexpensive, decent car to drive. It was out of service for 6 months in 2018 while it waited for an airbag replacement. Besides replacing the parts trying to find the idler pulley noise last year, I haven't had to do much.
I have owned it since 30k miles. I have struts on the shelf in the garage, waiting to change out on a nice day. I'm sure that will make a difference with ride quality. The brakes are original, and I'm sure they are due for pads/rotors/fluid. I have replaced the passenger side axle (dealership), throttle body, valve cover gasket, battery, both headlights (driveway repairs), and tires.
The throttle body and battery both made a difference in the transmission's sometimes erratic shifting.
It gets right around 30 MPG with mostly highway driving. The Camry I drove as an airbag loaner was a nicer car, and got 40 MPG, pencil and paper figured. With gas hovering down to $2.00 a gallon, the Mercury is less expensive to drive (factoring in the tiny amount of annual depreciation for my Mercury) , and easier to get in and out of.
When my Merc had 80k miles I read a bunch of stuff about EPAS failures and transmission failures. I thought about getting rid of it, but I'm glad I didn't. I hope yours works out as well as mine has.