Greetings Technical Discussers! Can we discuss a technical issue with a 2010 Legacy H6 engine? I ask because it could happen to the H4 engine too. I'll get to the point...
The check engine light (CEL) is illuminated due to code P0305 which means the ECU has detected a misfire in cylinder 5. Off-idle and low-speed stumble confirms this even after clearing codes. And then the CEL lights/flashes again (other warnings also light/flash due to safe-mode disabling of some options but they become irrelevant in this case).
I'd like to hear from your lessons-learned in correcting a cylinder misfire, intermittent or otherwise. When did/does it happen? What did/would you do to find it? What did you find? How did you correct and confirm the solution? How long did it take? How much $$$? ...
not sure if it's relevant, but that's what my 4 cyl turbo (EJ255) started throwing before baking a valve. Injector was apparently weak and leaning out the cylinder.
Zombaja, Thank You for this. And yes, it's relevant. I'll add "dirty injector" to my list.
There's a trick an old timer taught me long ago and I've used it across eight different vehicles to-date with very good results. I'll start this treatment-trick on this car with the next tank-load. Marvel Mystery Oil added into the fuel at a ratio of 4oz/10gal for every other tankful should help to prevent any more sticky/clogged injectors (going forward). It may already be too late for cylinder 5 but I'll find that out soon enough.
Any idea if/how the coil pack fault was related to the problem overall? Were there two problems that just revealed themselves at roughly the same time? Since the fault moved with the coil pack, that appears to be directly related to the problem...
Anarchy1024, There may also have been a defective coil-pack at play there. Swapping the cylinder 5 coil with cylinder 3, that was only step one in peeling the onion. I believe the real truth here is that the coil pack issue was simply a misdiagnosis, that the tech leaped to the conclusion on the short term result, as it was determined later that there were random misfires occurring across the entire odd cylinder bank. It wasn't long (two days or 150 miles had elapsed) before the CEL lit up again (coded P0301). The subsequent round of deep-dive diagnostics revealed the sludged oil OSV valve condidion as the true root cause.
Zombaja, I still do not know what the abbreviation "OSV" stands for. It's likely that "oil" and "valve" are the first and last words. I want to say "strainer" for the letter "S" but that would be (humorous) guesswork in retrospect - it's more likely to be Oil Steering Valve. One of my mechanical engineering buddies inferred that the flat H-6 engine needed help with directing/channeling oil flow (discovered during the prototype development stage) since they could not adequately deliver oil to the cylinders, or rely as much on gravity to return oil to the pan or pump. Until I hear about it from Subaru engineers then this is a plausible enough explanation if ever I heard one...
I never knew it existed before you mentioned it, so I don't know if it makes sense to it as preventative maintenance. $120 from Subaru, $90 from Amazon... kinda above the threshold of what I'd consider cheap enough to replace since I can.
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