After a tune up, R&R spark plugs, air filter, cleaned MAP sensor, coolant hose fix, PCV valve cleaned...everything went extremely well. While getting a very smooth running engine up to operating temp to check for any leaks (ran AC on full, then heater to make sure coolant levels were full and engine at normal temp) the engine went from smooth idle to surging slightly RPM up and down and running a bit rough. Check engine Light flashed so checked codes and found random misfire and a code for cylinders 2, 4 & 6. (front bank) Checked all vacuum connections, electrical & anything else I might Have disturbed during the tune up. I'm guessing there is something now going on that is affecting only the front cylinder bank but I'm not sure where to look as the back bank (1,3,& 5) seem to be fine (no codes anyway!) Any incite on what to run down first as I feel there has been a change in fuel mix due to a vacuum leak maybe to the front bank? Appreciate any response or suggestions on where to proceed next!
Thx,
Dave