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You need an expert opinion from the dealership on why the IAC failed, and if possible you need to keep the bad part. You may be able to sue the first shop in small claims court.
@SDWH, the dealership mechanic said that I should go back and talk with the shop, but was unwilling to put anything in writing. Unfortunately, I did not ask for the old unit back from the dealership as I thought at the time that it would be difficult to prove by me vs a mechanic from the shop, even if the circumstantial evidence is strong. So I am focused at this point at solidifying the facts to write a review to help other customers.
I just found an old post on focaljet that seems to explain clearly what happened!
As posted by axOn: Here’s the deal, there was some gummy crap in my TB and when I sprayed it down, it actually dissolved in the solvent that I sprayed (CRC Fuel Injected TB Cleaner) and then evaporated, leaving this tarry crap ALL IN MY IACV [It’s located on the underside of the Intake Manifold, right underneath the throttle body.]. And it gummed it “permanently open” - [resulting in a 4000 rpm idle]
I am not an mechanic, but this seems to be pretty convincing scenario of what happened to me.
Furthermore, a few other posts suggested that Ford has a special coating and recommend against spraying solvents into the intake and throttle body. If anyone can help me get an official document on this and if it’s applicable to 2.3L PZEV Focus ZX5, I may have the evidence needed for a small claim court case.
http://www.clublexus.com/forums/maintenance/118934-how-to-perform-induction-service.html
gserep1: Ford has mandated that the throttle bore NOT be cleaned with anything because the inside is coated with plastic.
Get Dirty Section: There are three reasons why you have to be careful, both in choice of solvent and in application: First, if the throttle body has a protective coating (as on many Ford products) to reduce the buildup, a strong solvent and hard brushing will remove it, so you’d have to do the job more often. If you see a warning label on a Ford product, that’s why.
I would think that the Ford dealership could give you the documentation on the PZEV engine that the throttle should not be cleaned with solvents. It should be in their service manuals. Also, if there really is a sticker on your throttle body saying “do not clean with solvent” then you just need a picture of it. If you can’t get to the throttle body on your own, a mechanic may be able to help you get it apart.