1996 Chevy Blazer woes

I have a 1996 Chevrolet Blazer 4x4,2-door, LS. 4.3 liter. Some days it runs fine, other days include hard starts (long cranking time) and if it is hot enough outside the car will stall out almost like it is running out of fuel on longer drives 45 mins +. If you let it sit 20 mins or so it will restart and drive ok for another 30 mins or so, then it starts stalling again. What do you think? The dealer is stumped.

Did the dealer have it when it would not start or continue running? That will be less likely all the time at this time of year unless you drive to South America. Did they consider the fuel pump or the fuel pump relay?

They did not have it when it stalling on a hot day. They did have a chance to witness the hard starting problem and they did change the relay, but the problem still exists.

Some sensors can cause this. There are reports that when a certain sensor gets hot, the engine will stall, or not start. The VSS (Vehicle Speed Sensor) is one. Another, is the crankshaft position sensor. When an engine is shut down, the engine block is hot, and it doesn’t have engine coolant flowing through it to carry the heat away. The heat goes into the sensor, it gets hotter, and it’s resistance changes, or, its internal wiring opens. As a result, no signal, or a wrong signal goes to the computer, and the engine doesn’t start, or, it stalls. The crankshaft position sensor could be removed, and its resistance tested, while it is heated, hotter and hotter, in a container of hot water. If its resistance reading is wrong, or it opens (infinity ohms), it’s defective. The VSS can’t be tested this way. It’s a generator.