Guys my GMC is giving me a fit. It seems to run fine for approximately 20 minutes and then starts to load up with fuel, mis and carry on. Black smoke just rolling out the pipes. It proceeds to shut off, and then will not start for 10-15 minutes leaving me stranded. While cranking the thing to restart it, you can smell oodles of unburnt fuel, and when it does start the check engine light is not on long enough for me to even attempt to get a code. I replaced the EGR valve hoping that would fix it, but nothing. It is a 1994 GMC Sierra with 5.7L.

 

engine coolant temperature sensor is/was the problem!!