my engine light comes on and off as it pleases lol, i put the scanner on and it said their isa misfire incylinder 3 then it went off after i changed plugs and wires then it came back on and said misfire in cylinder 6,the wire came off, put it back on and now the engine light goes on for an hour or two then turns off and back an forth, it also shakes bad when im sittin at a light or idiling, any suggestions would be great. im new to blazers, i drive a 99' blazer trailblazer ed. 4dr. auto, and dont know too much bout them

 

When was the last time you did a full tune up on the engine? Random misfires are typically tied to worn ignition components (cap/rotor and/or wires).

I would replace the plugs, wires, cap & rotor as a starting point. Maybe clean the MAF, EGR, and throttle body (including the IAC valve & bore on the TB).