for the last couple months my engine has been making a loud clicking sound. the sound speeds up and slows down with the speed of the engine and i can hear it if its in idle and i have my window down.

last night i decided i wanted to figure out what it was so i put my ear close to the engine to find out where it is coming from.

it seems to be coming from the 3rd cylinder, or around there. i put my finger on the fuel line for that cylinder, and i could feel the pulse very distinctly. i could feel it on the other cylinders as well, but it wasnt as hard.

could this be my fuel injectors? should i have them adjusted? if thats what i need, is it a job i can do myself?

thanks alot

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1991 300 D 2.5 Turbo, 220k
also in the family:
1981 240 D 185k
1991 350 SD 185k
2006 S 500
2005 SLK 350