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Current mileage is 107k.

A month back it gave me a light show. CEL and traction control lights on solid, Cruise and Brakes lights flashing. Happened after a refuel, and it eventually self-cleared. The light show cycle repeated 4 times, always seemed close to refueling. I checked the Forum, figured it was a gas cap issue. Thought about getting a new cap or a new seal.

Late last week it reoccurred. Then yesterday added a flashing CEL and a stumble like a misfire; the flashing CEL and misfire stopped on their own, but the lights don't go away this time around. Plugged in the OBDII and it says: $7E8 with Stored/Pending/Permanent DTCs of P0302, P0304 and P0306. No other DTCs. What common point can cause the whole left bank to misfire?

I checked the forums and noted several things. Timing (the chain is the original and is due for replacement). And the lower left OCV/Oil Control Valve (proper name: Oil Flow Control Solenoid Valve?) is mentioned as a suspect, but no related DTC appeared; would it?. Fuel (injectors) and Spark (plugs and coils) seem less likely to have three crap out all at once; is there a common fuel source/rail?. I'd prefer the OCV, but that timing chain replacement is due.

Any well educated thoughts to share?
 

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I was getting the same codes, then I got one for cylinder 4, while on vacation. Had to have to towed to a repair shop. They replaced all plugs and coils (OEM). Cleaned Throttle Body and injectors.

Car runs beautifully now. If you can do this yourself you can save $$,

Good luck!
 

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There is a common fuel line to the injectors - and a common fuel evaporation line from the injectors. At some point they split between the banks... the troubleshooting chart for the H6 motor and those DTCs doesn't have that in the workflow.

Here are things from the workflow:
  • Checking the voltage to and from the injector, checking the harness from the ECM to and from the injector (both voltage at different points and resistance if there is no voltage).
  • Checking the camshaft position sensor (that could do it for all 3 on one side) - (it's making sure they aren't loose - 2 per side, one bolt each, torque is 4.7 ft/lbs)
  • checking the crankshaft position sensor plate (plate rusted or teeth on the plate missing/broken)
  • checking the installation of the timing chain (making sure it's lined up with it's marks, hasn't jumped a tooth).
  • checking PCV valve and PCV hose
  • Checking intake for leaks, cracks or discoloration of hoses.
  • checking the plugs, wires, coils, injectors if nothing else shows a problem
The issue with the OCV (oil control solenoid valve) harness was some motors had a AVCS switch that can let oil seep past, and it would trip DTCs for the AVCS (active valve control system). The harness would get oil soaked. The TSB I saw was later years though - 2013-2019 cars. Without the AVCS DTC errors might not be as likely the culprit.


I'd start with air leaks in the intake - look for cracked hoses or parts of the intake on that side. Then check the camshaft position sensors aren't loose (the one bolt on the intake side one and exhaust side one should be snug).
 

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Someone correct me if I'm wrong but I remember reading or watching a good video somewhere about how a bad misfire in one cylinder can lead to error codes in adjacent ones. Something to do with how the engine actually calculates misfires.

So although it is weird they are all on one bank, it may be possible that it is just really bad on one cylinder from something like a bad coil pack or something.

FWIW I had my cylinder 5 coil pack (2010 3.6r) go bad and it only threw a single code for that specific cylinder. I also detected it early on however and actually struggled to even get itn to throw a code - something to think about.
 

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How old is the battery? No, I'm not kidding.
Same with the condition of the battery cables.
When did you change the spark plugs?

Multiple misfires on one bank can be a multitude of things. Power supply, cam system (actuator or solenoid), timing chain, spark plug wear to name a few.

These boxers balance themselves from opposing cylinders. You could have a problem on both banks and the computer is only picking up one bank.
 

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How old is the battery? No, I'm not kidding.
Same with the condition of the battery cables.
When did you change the spark plugs?

Multiple misfires on one bank can be a multitude of things. Power supply, cam system (actuator or solenoid), timing chain, spark plug wear to name a few.

These boxers balance themselves from opposing cylinders. You could have a problem on both banks and the computer is only picking up one bank.
Battery was replaced in early 2018.
Cables appear okay, no corrosion at connections/ends.
Plugs have about 50-51k on them, dealer talked me into replacement a little before 60k while doing some recall and other work. So they are due and on my list to replace.
Timing chain is original, so at current mileage it's about due for replacement.

I want to do what I can before handing it over to the pros. I don't know of a good Independent shop in the area, and of the two Subaru dealers I've had less than stellar work from one, so the timing chain replacement is probably going to the other.
 

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Battery was replaced in early 2018.
Cables appear okay, no corrosion at connections/ends.
Plugs have about 50-51k on them, dealer talked me into replacement a little before 60k while doing some recall and other work. So they are due and on my list to replace.
Timing chain is original, so at current mileage it's about due for replacement.

I want to do what I can before handing it over to the pros. I don't know of a good Independent shop in the area, and of the two Subaru dealers I've had less than stellar work from one, so the timing chain replacement is probably going to the other.
the timing chain shouldn't need replacement unless there is a problem with it.... it's not a maintenance item like a timing belt.
 

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the timing chain shouldn't need replacement unless there is a problem with it.... it's not a maintenance item like a timing belt.
Thank You! Too many Toyotas in my past and I was thinking it was due for replacement around 120k. I'm certain everyone (Indy or Dealer) would have declined and set me straight. I probably also saw the belt replacement timing and had that number in my head. Thanks again!
 

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Thank You! Too many Toyotas in my past and I was thinking it was due for replacement around 120k. I'm certain everyone (Indy or Dealer) would have declined and set me straight. I probably also saw the belt replacement timing and had that number in my head. Thanks again!
oh yeah... I've replaced enough timing belts to appreciate not having one :)
 

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On the battery: I have a regular customer with a 13 Forester, EJ253, and he bought a new battery to replace the original when the car started doing weird things. Someone else in the shop put the battery in for him, (he doesn't have tools for it), and he went on his way. He called me a couple days later and said the car would start then shut down. It did it 4 times in a row then ran fine. Did it again later in the evening when he left the gym. I got under the hood after looking at the codes, (a few communication codes on different modules with an ignition circuit code on the ECM - no warning lights on), and went straight to the battery and checked the tightness of the clamps with a socket. Both were tight. I grabbed the ground clamp and it moved on the negative post. I pulled the clamp, removed the plastic isolator from the clamp and reinstalled it, tightening it down. No movement. Car fired right up and over the past 3 days he hasn't had a problem.

Looks can be deceiving. A tight nut on a clamp can be deceptive also. Not all batteries are made the same and the slight difference in post thickness made the difference in good conductance over bad.

Battery brand and size is also a factor. If you have a battery from Subaru, chances are good that the battery isn't the issue. From somewhere else, depends. If it's Auto Crap, it's a trash battery. If it's WalMart/Sam's it's 50/50, (I haven't been able to determine with certainty that the WM/Sam's batteries are causing issues).

Another thing is corrosion can be under the insulation and you won't know it.

The best way to test the cables is with an Ohms meter or an amp gauge tester. With an Ohms meter you want to see .1 Ohms or less. With an ammeter, the ampere output should match or be higher than the battery is rated at. Ampere output of a battery is tested cold and without the engine running. Then you check to see that you are getting within 75 amperes or so by just moving the ground side of the tester to the alternator case and check flow again. If it's more than that, especially if it's over 100A, somewhere you have a weak ground.
 

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I had this same problem on my 2010 3.6 Limited with approximately 120K miles... the light show happened for the first time in August 2018, shortly after having the spark plugs replaced (by my trusted mechanic of 15 years). I took it in and the codes read misfire in 2,4,6, and the recommendation for the codes was to replace the spark plugs and coils. The new spark plugs were checked and were fine (some brand that is high quality but I forget what it was, but not Subaru parts). Mechanic said the coils were fine. In addition to the lights going off, I began to notice the engine kind of "chugging" at times, or hesitating, or something... Maybe it was indeed misfiring? I'm not sure what that would feel like, if anything.

The light show would then happen randomly after that first time over the next year (every couple of months; I never noticed if it was after filling the fuel) and every time the codes read misfire in 2,4,6. Sometimes another (seemingly random) code would come up, but my mechanic could never find anything really wrong. And still the random "chugging" thing that I would notice while driving on the highway. Of note, this light show only happened during highway driving - never when driving around town.

My mechanic would do some looking around (he considered a couple of the things you mentioned - e.g., oil control valve), clear the codes and send me on my way. I can't remember everything he suggested could be the problem, or everything we tried. At one point we were worried my engine was leaking oil, but that turned out not to be the case. I never spent more than a few hundred dollars, and sometimes I didn't spend anything. We eventually replaced the coils with Subaru parts, and that was about $1200 (even though he said my coils were still fine). After replacing the coils, I still got the light show one more time, and the same codes came up with one additional code - something about the cam shaft position? My mechanic said, "well that could be your problem." He said he was 75% sure it was fixed. So, we fixed that camshaft position thing (can't remember the cost), and I was done at that point, since I would still feel that chugging thing at times (always on highway).

I traded it in last week for a 2019 3.6 Touring. I loved that 2010 right up until it needed to go in and out of the shop. Now that I have so many fancy features, I'm kind of glad I got to upgrade sooner than I would have normally (we keep our cars for 15+ years).
 
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