wiscoutback Posted February 7, 2020 Share Posted February 7, 2020 Hoping some friendly and knowledgeable folks out there can help me. I have a 2012 Outback with a 3.6 liter H6 engine and the check engine light is on. I drove it to an auto parts store to read the code and it came back as all six cylinders misfiring! A little history here - I purchased the car used from a dealership in Florida one year ago with 70,000 miles on it. While driving it down to WI, I noticed a brief, but fast vibration coming from the engine between 3rd and 4th gear, usually when the car was under load. The engine would also hesitate when accelerating, especially up hills, but usually only did this when it was cold. I had it checked by a Subaru dealer and they thought MAYBE it was a failing torque converter? and gave me a pretty high estimate for shop costs on a hunch. I did some research online and decided to replace plugs, tube seals, and valve cover gaskets and have the fuel injection system cleaned. It took care of the problem for a few weeks, but now the problems are back and bad as ever. When the CEL came on, I was expecting to see a code for one cylinder misfiring, but it came back with a misfire code for all 6. Makes me think it's not the ignition coils, but something potentially worse... I would REALLY appreciate advice on ways to diagnose this issue. I really like this car and can't afford a new one! Quote Link to comment Share on other sites More sharing options...
idosubaru Posted February 7, 2020 Share Posted February 7, 2020 when you replaced the plugs and gaskets were there any oil leaks in the plug tubes or issues noted with plugs? I don’t think this is possible but could the COPs be on the wrong plug? How about the suggestion that never solves an issue - bad gas? Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted February 7, 2020 Share Posted February 7, 2020 (edited) how's the rust/corrosion issue look underhood? maybe refresh some ground connections and check alternator voltage. does the '12 manual suggest running high octane fuel? maybe the fuel pump is getting weak or there's a problem with the regulator? if possible, have a shop look at live data. maybe a:f is off or the ecu is retarding timing. Edited February 7, 2020 by 1 Lucky Texan Quote Link to comment Share on other sites More sharing options...
3Pin Posted February 7, 2020 Share Posted February 7, 2020 I was thinking fuel pump or filter as well. What type of plugs did you use? It wasn't setting check engine lights before the spark plug change correct? This isn't one of those flood cars is it? Quote Link to comment Share on other sites More sharing options...
wiscoutback Posted February 7, 2020 Author Share Posted February 7, 2020 3 hours ago, idosubaru said: when you replaced the plugs and gaskets were there any oil leaks in the plug tubes or issues noted with plugs? I don’t think this is possible but could the COPs be on the wrong plug? How about the suggestion that never solves an issue - bad gas? Very little oil noticed in the tubes and the spark plugs looked like they needed to be replaced, but nothing out of the ordinary. Everything went back together as it was. Sine this is a reoccurring issue I'm not quite ready to suspect the gas... Quote Link to comment Share on other sites More sharing options...
wiscoutback Posted February 7, 2020 Author Share Posted February 7, 2020 1 hour ago, 1 Lucky Texan said: how's the rust/corrosion issue look underhood? maybe refresh some ground connections and check alternator voltage. does the '12 manual suggest running high octane fuel? maybe the fuel pump is getting weak or there's a problem with the regulator? if possible, have a shop look at live data. maybe a:f is off or the ecu is retarding timing. No rust or corrosion under the hood. Good suggestions though. Gives me a few more options to investigate. Quote Link to comment Share on other sites More sharing options...
wiscoutback Posted February 7, 2020 Author Share Posted February 7, 2020 10 minutes ago, 3Pin said: I was thinking fuel pump or filter as well. What type of plugs did you use? It wasn't setting check engine lights before the spark plug change correct? This isn't one of those flood cars is it? I used the recommended plugs straight from Subaru since I was told it makes a difference with these engines. The check engine light was coming on before the spark plug change out. I don't think it was a flood car... nothing in the carfax about it. Quote Link to comment Share on other sites More sharing options...
3Pin Posted February 7, 2020 Share Posted February 7, 2020 I have had those types of check engine lights and one was the coil, the second was the fuel pump, the third on an h6 2003 was a fuel regulator. On the 03, there were two I believe, and the one that was offending gave rough running and CE cylinder misfire on that side of the engine. If both are bad or if there is only one on the 14, then that could be it. Very unlikely it is the coil as they are all individual and all are sending CE which would be very rare. It really sounds like a fuel pump/filter/regulator kind of thing. Quote Link to comment Share on other sites More sharing options...
idosubaru Posted February 7, 2020 Share Posted February 7, 2020 H6s occasionally have 6 misfires caused by carbon deposits/fouling of the intakes/heads. 1 Quote Link to comment Share on other sites More sharing options...
3Pin Posted February 7, 2020 Share Posted February 7, 2020 I have a 2014 3.6 and it has been a really good driving/running machine. change the oil, 1 airbag recall and that is about it other than the normal brakes, tires, engine oil trans fluid changes. Quote Link to comment Share on other sites More sharing options...
Numbchux Posted February 7, 2020 Share Posted February 7, 2020 Any other codes? In the FSM, the diagnostic for misfires on all 6 (the last of 21 diagnostic steps, but the only one that addresses all 6 cylinders) and no other codes is: Repair or replace faulty parts. NOTE: Check the following items. • Spark plug • Ignition coil • Fuel injector • Compression Quote Link to comment Share on other sites More sharing options...
bratman2 Posted February 8, 2020 Share Posted February 8, 2020 My brother got a couple of bad spark plugs out of the box new. About ran him crazy trying to figure it out because he "knew" the spark plugs where new. See if you can find some resistance specs on the coils and confirm all 6 are with in spec. Try a heavy dose of seafoam and see if that helps then check coils, then recheck plugs. Quote Link to comment Share on other sites More sharing options...
idosubaru Posted February 8, 2020 Share Posted February 8, 2020 Problem existed before and after spark plug change so unless the details described aren’t accurate it’s almost inconceivable to get 12 different plugs all which have the same symptoms. it might be worth asking the condition of the old plugs and pull one or two of the new ones to check their current condition. Quote Link to comment Share on other sites More sharing options...
wiscoutback Posted February 9, 2020 Author Share Posted February 9, 2020 Thanks for the responses. CEL came on again today - codes 301 -306 again. I can't find the pictures I took of the old plugs, but nothing too crazy there as I recall. A little dark residue from sparks, all looked the same. If I'm feeling spunky tomorrow I'll remove the plugs and take a look again. I'm going to do the seafoam treatment into the intake, unless there's any reason I shouldn't... Maybe this will clean off some of the carbon deposits. I'm hoping for low cost solutions that I can do myself! I've never checked for compression, injector signature or resistance testing, cylinder contribution test, a-f ratio test, etc. before, but I'm willing to do some work if it will help me diagnose the problem. Any suggestions on cheap and easy ways to do this, I'm all ears. I'm pretty handy and willing to do some work, but I just don't have the garage setup to drop the engine and start rebuilding the cylinder head assembly... One thing I forgot to mention but might be relevant - The engine has been using up oil internally at the rate of about 1 quart per 1000 miles or so. No external leaks. Could this be related? Quote Link to comment Share on other sites More sharing options...
Ferret54 Posted February 9, 2020 Share Posted February 9, 2020 Does this have an EGR? I had sticky EGRs on a few EJ250 engines ( 98, 02, 04 ) and they caused rough idle and misfire in all cylinders. Just a thought as I read this thread. Quote Link to comment Share on other sites More sharing options...
3Pin Posted February 10, 2020 Share Posted February 10, 2020 if it is using up 1 qt of oil per 100, you should go to a dealer and have them do an oil consumption test. I think that yours might be on the list. I still think you need to check for fuel pressure. it could be a clogged filer, bad fuel regulator or fuel pump. Lack of fuel can cause these symptoms. Quote Link to comment Share on other sites More sharing options...
idosubaru Posted February 10, 2020 Share Posted February 10, 2020 Change the PCV valve with a Subaru one to maybe help mitigate that oil loss. easy and cheap. another user with an H6 that had all 6 misfires, had three dirty injectors on one side. Cleaning the 3 on one side alleviated all 6 misfires. its loosing oil, usually past the rings, but this is fairly common without causing all the cylinders to misfire. 2 Quote Link to comment Share on other sites More sharing options...
Numbchux Posted February 10, 2020 Share Posted February 10, 2020 6 hours ago, 3Pin said: if it is using up 1 qt of oil per 100, you should go to a dealer and have them do an oil consumption test. I think that yours might be on the list. Not on a 6-cylinder Quote Link to comment Share on other sites More sharing options...
3Pin Posted February 10, 2020 Share Posted February 10, 2020 I looked and it is not on the list. The 2013 2.5 is. Quote Link to comment Share on other sites More sharing options...
Rampage Posted February 12, 2020 Share Posted February 12, 2020 I found this in the FSM. Hope it helps. It shows 6 things to check that can cause misfires on all 6 cylinders. Quote Link to comment Share on other sites More sharing options...
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