01 Forester AT 2.5L check engine light came on flashing today, ran a code scanner code came back P303. Earlier in the year the harmonic balancer was loose and threw off the timing, got a balancer repaired the crankshaft re-timed and good to go. When I saw the code I thought "Snap" and went to the balancer and timing again; all good on those fronts. Worked down the list of usual suspects, injectors have good resistance and are lifting (DMM and Mechanic Scope). Fuel check; next fire. Checked plugs and wires all good on visual continuity and resistance. Tad bit of oil high on the collar of wire 3, not enough to cause a misfire in my opinion (let me know if I am wrong on that). Got to cylinder 3 with the spark tester and no FIRE!? Which is really weird to due to Subbies using waste spark. Tested and rested to be sure (ie swap plugs and wires in multiple configs) still no fire in three. Ran resistance test on the primary and secondary coil it is within range according to the manual.  Ran to autoparts store where I got the coil and they will warranty the coil, though I had to purchase it; then be reimbursed upon returning the defective unit. Scooted home plugged up the DMM and both coils read more or less the same with small variations; installed the new coil and like Tom Hanks we have fire. Will double check everything tomorrow, my question is should I be looking for another culprit?  With how the Subbie is set up it is kind of odd, to have no fire in one cylinder. 

Thanks, HH

 

Oil can definitely cause a misfire. Not certain qualitatively where/how much/how severe etc.