1989 190e 2.6 with 120,432 miles and burning oil strong

Let me describe the symptoms:

sound made during acceleration from 15mph to 38 mph

light or heavy acceleration

goes away if let off accelerator or pass 38mph

the car sounds like a diesel, sound appears to be coming from the engine bay.

that's the best description i've come up with that offers the most info. I know it's hard to diagnose sounds on cars without actually hearing them, but i'm trying to get a starting point. at first i thought the timing chain might need adjustment, but it only makes the sound during that interval and not all the time, not sure if that could still be a possibility. It's going to my mechanic on friday. Any input would be great.