Over the past month or two my 944 has developed an odd sound. It only happens at 3000 RPM, plus or minus a little bit when I'm accelerating through the gears. I'm not really sure how to describe it, its like a rumble or or a grinding noise. Just incase this might be related, when the engine is cold there is a audible tapping sound that comes from the engine. I would guess tappets but I'm not much of a mechanic. Hopefully running synthetic didn't hurt the motor. The car runs great so I'm not worried about my engine exploding at present, but I would like to have some idea what is going on so its not always at the back of my mind. Thank you.
Rick
86 Porsche non turbo w/ 104k