My number one injector is nailing/clacking quite a bit upon start up, and then again when accelerating. Once the engine is nice and hot I don't seem to notice it at as much. The nozzles are new on all 4 injectors, so i don't know why number one is acting up. Perhaps I just need to replace the whole injector? If so, can I only do one of them or would I need to do them all?

I don't use any diesel additive. Perhaps I should see if that helps lubricate the injector and ends the nailing?

I appreciate your thoughts...