[Cidcrash]

1989 2.5 iron duke 215,000. Replaced water pump, tensioner and serpatine belt. 2 weeks later the alternator started whining so I swapped that a few hours ago. Now the idle went from 8-900 to 11-1200. Think previous owner could have cranked up idle? Runs a lot better with new alternator 🤷‍♂️

 

[ShadeTreeMech]

I'd guess it's the IAC. That or you have a vacuum line off.