What causes my engine to idle very high? on 2005 GMC Savana 3500

Tried MAF sensor, upper intake gaskets (possible vaccum leak), IAC (had to change whole throttle body can't buy IAC alone). Unable to find any vaccum leaks.

Get Your Car Fixed at a RepairPal Certified Shop.
We certify shops based on expertise, quality work, and verified customer reviews
1 answer
Check the alternator.