I have a 2000 blazer with a 4.3 vortec, when the truck is cold it hitches like its losing its fire although it is not actually losing fire, once the truck warms up or if you shut it off and start it again, it runs like a top. I have replaced the rotor button, cam sensor, distributor cap along with new plugs and wires, but nothing seems to help! I have been told that it is the crank positioning sensor and I'm wondering if this true before i change it!?!? any ideas will be appreciated

 

Unless the check engine light is on, a DTC is present for the crankshaft position sensor, and after following the flow chart it instructs you to replace the sensor, DON'T replace it. If the crankshaft position sensor or timing cover is moved, removed, replaced or disturbed in any way, the crankshaft position sensor relearn MUST be performed using a scan tool capable of initiating it, (the el cheapo $500 scan tools won't do it).

Is your check engine light on while driving? Are there any DTC's in memory or pending? If so, what are they? Have you checked fuel pressure and leakdown? If so what were the readings?