I ran a can of engine flush through it as i suspected oil was in there much to long and i filled up with 5w30 and new filter no change in sound although the oil is so clear now i can bearly see it on the dipstick! I think its the timing causing det but its there at idle sound dieselish, i might buy a comprssion tester next if the retiming doesnt help, i had a small end gone once in a mazda 323 it sounded similar but much worse when revved so im unsure, previous owner stated its been making this noise 1.5 to two years and has never gotten louder but is annoying