I am having the EXACT same problem with my car. It makes a taptaptaptaptaptap when doing anything in drive, and if I free-rev in neutral, it'll start to make the noise around what I guess is 2000-2500 RPMs as well.

I'm getting ready to do my fuel injectors (ordering the injector socket, bought myself a torque wrench, etc.) and hope that helps...if not, I'll probably have to have my indie replace the timing chain and associated components.

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1983 Mercedes-Benz 240D
Automatic, A/C, Power Sunroof, Power Right Side Mirror
231K Miles FOR SALE MAKE OFFER