On Tuesday I was headed out of the mountains and out of nowhere this very hard knock started. Sounded like from cylinder 1, 3 or 5. I imeaditally look at my oil pressure guage and it was fine (60 - 70 psi, don't remember exactly). I did happen to notice that my "tinkerbell" noise was also present. Then as quick as it started it was gone, maybe 5 - 8 seconds (I was just about to turn the engine off). The knock returned the next morning for about 3 - 4 seconds, It has not returned since. I checked my oil level and it is fine. I guess I'm wondering if an injector can come and go like that???? /forums/images/graemlins/confused.gif I am working torwards getting my injectors rebuilt / replaced, but is this a sign of not much time left or is there something else? Thanks in advance!