My 1995 Blazer.4.3 Vortec Shuts off while I am driving it. It seems to do this do this once it has been running for a half hour so. I was able to get it home but it quit on me 4 times. I waited like 5 to 10 minutes before I tried to start it and drove it home before it quit on me again. After the engine is cold it starts fine. I had the timing chain cover replaced over the summer. After doing some research I was told it could be my crank shaft sensor and if the sensor is ok I maybe able to shim the sensor. Pulled the sensor noticed a scuff mark on the sensor. I added to thin plastic shims to the sensor. Let it run for a a hour or so in my driveway and no problems, I thought I had it fixed, Drove 40 minutes on my way to work noticed the tack started to fluctuate around 2000 RPMs. On my way home from work about 40 minutes the tach started to fluctuate and I lost power and the engine light came on. Had it towed and once i got it home it started up just fine and the service engine light was out. I am baffled anyone got some ideas.