One problem related to loud engine noise has been reported for the 2008 Jeep Wrangler. The most recently reported issues are listed below.
My Jeep Wrangler x 2dr was sitting from 12:15p the day prior to (was a nice day took my motorcycle around town) and at 5:30a I heard a loud noise that woke me out of bed. Ran upstairs & outside the truck was pouring smoke out of my hood. . . Than taking action my boyfriend unlatched the hood of a possessed truck (blowing the horn constant radio on lights on) and proceeded to disconnect the battery to yield/stop the truck from continuing to burn. Called the dealer and they sent someone out to do a claim on the Jeep and called me two weeks later saying they would not cover it because its not under manufacturers defect. The insurance company won't cover it either because we stopped the fire. . . Which I don't understand. Now after doing $3000 and upward of there in work replacing all the wiring (computer and fuse box) it still wont run. Helllpppp!.