My cuzin has a 92 Civic CX with a D15 engine. At around 3500RPM it makes a horrible rattling sound. I'm not certain it's 3500 because I have only listened to it under the hood, but it sounds like about 3500. Anyway it comes on and then goes off really quick, prolly within about a 250-300RPM band. Has anyone encountered this problem? If not, with the limited information I provided, could anyone provide a guess? I'm stumped.