My idler pulley came off while I was driving, so I don’t have the bolt anymore. I can’t find a good source to see what size bolt I need. I already bought a new idler pulley for my 2005 Chevy Trailblazer 4.2L LS 4WD. Any help would be appreciated.
You can type that into RockAuto along with your vehicle year, make, and model. They usually have the right parts listed.
They sometimes sell the idler WITH the bolt. Do some research on that because the bolt has special washers to center the pulley and space it properly.