my 1999 Blazer will cut off and stumble with no warning at no particular pattern. It will also stall or cut off at a stop light or stop sign, again, no warning or pattern. It is sporadic and driving me crazy. I replaced the map sensor and fuel filter but the problem remains. I'm all ears. Thanks

First thing you will need to know is if the truck is loosing fuel or spark.
Fuel systems on those trucks are known for giving some problems...check the fuel pressure..needs to be about 60 psi.
Also while the engine is running, wiggle the wires to the coil...sometimes they will break inside the insulation and cause intermittant stalling concerns.
There were some trucks with intermittant ignition switches causing problems also.
The most important thing is to perform a little diagnosis before you spend any money on a part that may or may not fix your problem.

also gm tech and i would also check the ground f0r the fuel pump it goes to what they call a ground comb and i have seen them melt.2 dr are located behind the rear bumper not sure where a 4dr is. also posible crank sensor it the bottom of the front cover

also gm tech and i would also check the ground f0r the fuel pump it goes to what they call a ground comb and i have seen them melt.2 dr are located behind the rear bumper not sure where a 4dr is. also posible crank sensor it the bottom of the front cover

Watch your instrument lights. When you turn the key to on, you get an array of lights, air bag, anti-lock etc.. If you do not see these when you stall or it when won't start, the ignition switch module is bad. Look through these post subject there are some good instructions how to change it. I just did it myself.