2000 blazer 4x4. I've had this P0300 issue for a while now. Replaced MAF sensor, fuel pressure regulator (was weak and bleeding off), fuel pump, fuel filter and it seemed to help a little but still occurs occasionally getting on the freeway. The MIL light will start flashing at about 3000rpm @ 60mph, freeze frame data was showing load value @ 40% open loop, fuel trims were all @ 0%... Computer maybe? I also just got an O2sensor P0147 bank 1, sensor 3 heater circuit malfunction. Can this cause the code? Cap, rotor, wires, and coil are next on the list to replace unless the injectors would be the next logical thing to do. Thanks for any suggestions

 

Not sure if the O2 sensor will cause the P0300 random misfire code. But I would start with the simple least expensive first: cap, rotor button, plugs, plug wires and check the ignition coil to make sure it is still putting out enough volts.

Make sure you stay with ACDelco with the tune up.

I done a tune up on mine because of the same code and used all ACDelco parts and I have not seen that code in over three months. But I also went ahead and upgraded my spider injectors (while i was replacing the LIM gasket).