: x So. I bought an 99 Audi A4 1.8 Turbo Quattro (manual) with about 100,000 miles on it about a few weeks ago. Unnoticed at first, it now has a knock (or always had a knock), mostly noticable at idle, but NOT noticable when engine is cold at first start up. I noticed it first after driving for about an hour on hwy, and had to stop at a car parts place to get epoxy for a windshield crack (yeah. That worked. Not). And I was parked up against a building and left my car running to go in. I don't notice it at all while inside the vehicle. (Unless you open the windows which I don't since I live in Michigan and it's October. So anyway. It knocks, my hubby is worried, and he sent me on a mission to find out what the problem is. He's a little upset. Please help. BTW, timing belt(chain?) Replaced 10,000 miles ago.