What is causing a rattle in my 95 Chevy Cavalier?

[Ash Nichole]

I have a 95 Cavalier (2.2 engine). The original engine was replaced and a newer (~50,000mi) was put into it. After it was replaced, there was a rattle/creaking noise just when I initially accelerated. Since then, the water pump, tensioner pulley, and serpentine belt have been changed. After I got the tensioner pulley changed the second time the sound did not come back for several weeks and then it started again. I had more work done to it and now it makes the sound when idling also. The noise disappears when it's in park and after initial acceleration. Does anyone know what the problem is? Also it's not the timing belt. Thanks!

 

[Halil Gungor]

Is your exhaust system tight, maybe heat shield, or loose something in exhaust system?