Merle Roberts

Howdy. I have an 83 DL wagon and just noticed a sound in the engine i've not heard before. When I am driving and have the gas pedal engaged it sounds smooth as normal, but when i let up on the gas to coast the engine start making a chugging sound, kind a sharp sound like 2 pieces of paper rubbing together. THen, when i press the gas pedal to pick up speed it smooths out again. Any ideas? Thanks.