I just replace sparks, plugs, EGR Valve, clean the entire EGR pipes, o2 sensors seems to be ok, the car runs roughtly, and i spot some bubbles at the coolant
Getting P0300, it used to be P0304 an change! on 1999 Isuzu Rodeo
May need to re-learn the crank sensor signal. You need a factory scan tool to perform this procedure. Correct spark plugs are improtant and the gap should be correct. Some bubbles in coolant could be normal if you are not loseing coolant or not overheating. If it is running rough I would try and disable spark to each cylinder one at a time to see if one of the cylinders is not contributing thus could mean a mechanical , fuel injection problem or an weak spark to a cylinder.
reset codes and drive
seek diag and est from your mech
Get diagnosed - possible headgasket leak. AFTER FULLY warmed up and system purged , bubbles ARE NOT NORMAL.