Brisco811, I'm curious which model iPhone 4 your wife has. Verizon? AT&T? Sprint? And when you said that her iPhone 4 "works perfectly", does that also mean little things like the phone rings properly with an incoming call using Nissan bluetooth?
Also, do you have the same iPhone model as your wife?
I ask, because I think the problem began with iOS 4.x, but I have always used AT&T iPhones. When I had my iPhone 3G with iOS 3.x, I had NO problems with my 2007 Sentra's bluetooth. When I upgraded my 3G to iOS 4, the bluetooth problems began. It hasn't been fixed with iPhone 4 using iOS 4.x or iOS 5.x. So, I think the problem started with iOS 4, and has never been fixed, but wonder if its limited to AT&T iPhones.
I'm about ready to give up on this problem, because I think there's nearly ZERO chance it will be fixed.