chain

My 240 has been idling irregular for the past couple days. I took out the aiv like recommended by some. It didnt fix the problem. I opened the hood this morning and i hood a small sscrapping like sound coming from the engine. I recently fixed nd put in new parts for the bottom timing chain so it cant be that. But when i put it back together the top chain was a lil loose but i left it because when i cranked the engine it would tighten by oil pressure. JW if it is the top timing chain that could be causing my problem.