I was driving to a buddy's house today and the motor developed a pretty loud knock:(. It happens in neutral around 1500rpm, and in gear around 2000 rpm. The odd thing to me though is, is that while in gear, If I put it in first, it happens at 2000rpm, in second, 2000rpm, in drive, not till 3000 rpm. Any ideas are welcome. The car is going to the shop in the morning but Im just trying to find some kind of relief I guess you could say. The car is a 1994 Z28 A4. Im thinking possibly a lifter noise of some kind, possibly rod knock, maybe bad flex plate, bad tourque converter? I have no idea but whatever it is Im hoping its not super expensive. Also, this should help, there is a fair amount of blow by comming up into the passenger side valve cover.

You may have a bad valve in the heads. Pull the valve covers and see if any valves are not bent or if there and no bent push rods.

ok...pulled off the valve covers, loosened the rockers and inspected all of the pushrods. Took them inside and rolled them on the work bench, none are bent. As far as valves, Im not 100% sure on how to check that, but, from the looks of em, they seem to be going up and down, no side to side, no weird movement from them, I also dont really hear it in the valve covers, as well as I do on the top of the intake manifold. Im really starting to think lifter at this point. If I were to push on the pushrod, would a crush/collapsed lifter let the pushrod push in, or would it not move. Because thats what Im trying right now. Ill be back in, in about 15 minutes to post up what I found.