2001 blazer engine problems

Hey i just got a 2001 blazer zr2. My check engine light has come on and i took it to a local shop to get it checked out and they didn't come up with any problems...they said it must be an electrical problem. also, sometimes when i drive for a long time such as highway driving the engine seems to become very weak...it seems as if only half of it is running....it feels as if it has half the horsepower...and soemtiems it kicks back in and accelerates as normal. Does anyone know what this is- and is it a significant problem?thanks- Matt

i also forgot to say that when this problem happens, it doesn't shirt at the right time and sometimes doesn't shift even close to the normal RPMS....

Go to autozone and get the code read properly.

The code is the key to your problem.