Pewter_LS1

If this thing is faulty or starting to go faulty what would the signs be? could it cause the car to run wierd i.e stall? kinda hard to start after a stall? right now Im habing some issuse's that Im trying to resolve..I have done a few things but it started with a crankshaft postion sensor that went bad..changed it had the car pcm reflashed..cleared it up for a day..then I went in and tightend the cam after someone told me the cam was loose..Im not getting any codes..car will run fine then all of a sudden rpm's drop to zero car kinda idles real low/rough..give a little gas it hesitates as if its not getting any fule or exactley like a bad o2 sensor(they are good) after about a minute rpm's will resume and it runs fine...could it be the tach sending unit ?