I REPLACED THE ENGINE AND NOW IS RUNNING TO ROUGH, P0300 WITH NEW SPARK PLUGS on 2001 Mazda Millenia

I REPLACED THE ENGINE AND NOW IS RUNNING TO ROUGH, P0300 WITH NEW SPARK PLUGS, BUT SOME TIMES IS RUNNING JUST FINE AND THEN THE CHECK ENGINE LIGHT CAME ON AGAIN. SOMEBODY CAN HELP ME?

by in Waco, TX on September 25, 2011
2 answers
ANSWER by on September 25, 2011
Check ur connection on the ignition coils,the code that u have its when u got more than one cyl missfiring
ANSWER by on September 25, 2011
check the wires and the coil. was it a new motor or used?? Roy