This may have been discussed before but I haven't seen it. So, here goes.

Starting about six month ago I could hear a buzz between shifts. At first it was only when the car had been warmed up. Then it got to where I could hear it during every shift. Recently, I could hear it during engine operation on the road when the rpms were between 2500 and 4000. So this began to worry me.

The car is an 03 Evo, 102 K miles, plain stock with no lifter noise.

The first thing I thought to check was the turbo and shaft play was normal. Then I replaced the two idler pulleys on the accessory belt and checked out the other pulleys. Everything was good there.

That left three possibilities, valve noise at rpm, bearing noise and timing belt problems. For some reason I thought it had to be a b-belt problem and pulled the timing cover. It was, the tensioner pulley for the b-belt could be spun freely by hand. This car has 40K on a timing belt job. I did it and the b-belt was tensioned properly. Anyway, retensioned and no more buzz.