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Good Morning,

 

I have a 2011 outback with the 3.6R engine, 47,700 miles.  It is misfiring (cylinder 5 mostly, sometimes cylinder 6) under the following conditions:

1. Under load, for example when climbing a hill

2. At idle when the transmission is in drive. (It does not misfire when the transmission is in park)

 

So far I have replaced the air filter and cleaned the MAF sensor.  Also put two bottles of drygas in the tank (the tank was already full)

 

We have owned the vehicle since beginning March 2015 and had no problems whatsoever up until 4 days ago.  The gas tank had just been filled and the car sat over the weekend.  On Monday the misfiring started.

 

Have new spark plugs and plan to check the coil paks by swapping.  However, I need to know which cylinder is #5 and #6.  So here are my questions;

 

What is the cylinder layout for the 3.6R?

Where can I get a good service manual for this vehicle (I have looked at alldatadiy)?

Besides the plugs and coils, what else do I need to check (injectors?) and how would I go about doing this?

Can anyone recommend a code reader for Subaru vehicles?

 

Thanks for your help,

 

Eric

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Cylinder lay out:

Back of car

56

34

12

Front of car

 

Those H6 plugs generally are robust and last a long time with little wear, it would be odd for it to be them.

I'd pull the most egregious plug and check it for oil - if the spark plug tube seal leaks it can get oil down in the spark plug well and cause misfires.

 

And yes - install new plugs, an easy first step.

 

The service manuals are often found online for free, i've got dozens of them, none as new as yours but i haven't looked for any that new.  the H6 engines are largely the same, i would guess any 3.6 manual is going to help you tremendously unless maybe you're getting into wiring diagrams - but procedurally they're very similar.  plugs, maintenance, the engines are probably swappable to the first EZ36 ever made...etc.

 

code readers -

i like the cheap ebay ones so i can use, abuse, throw it around the garage, and let people borrow it and not care about it.

you can buy bluetooth adapters that are sweet

you can get laptop cables that plug into OBDII ports and use FREESSM and/or ROMRAIDER for excellent diagnosis...and it's all free minus a cheap cable

or buy an expensive scanner

or get the Subaru scanners for $5,000

 

whatever floats your boat and works best for you.

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i'm not suggesting use this link but for instance i found this in about 15 seconds on google:

http://jdmfsm.info/Auto/Japan/Subaru/Legacy%20Outback/2011/

 

easy stuff like where to get an FSM and cylinder locations can be found on google in seconds.  a little proficiency there will improve your diagnosis/mechanical abilities orders of magnitudes.

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Thanks for the info.  Very helpful.    I have been searching on google for awhile and found some information, but not all that I needed.  I guess I need to try some different key words.

 

Always something new to learn.  

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Thank you for the additional input on the misfire issue.  I will be working on it today.  Was able to download pertinent parts of the service manual based on the lead from grossgary.  Awesome link by the way.  Will definitely be looking at the coil paks as well as the plugs.  When I drove it yesteday (about 50 miles) I was checking the codes throughout the day with a borrowed code reader.  Cylinder 5 only came up right away.  By the time I got home it was throwing misfire codes on cylinders 5 and 6.  Have yet to see misfires reported on any of the other cylinders.

 

I agree wholeheartedly that it is much too early for failure in the ingition/fuel delivery/compression systems of this vehicle.  Up until a week ago, this car ran beautifully.  Took hills like nothing (we live north of the adirondacks), got good gas mileage (around 24 mpg), and lots of power whenever required.  Carfax showed it was well maintained (regular oil changes/servicing).  That's what concerns me; that the misfire cause(s) is something out of the ordinary.  Not just a simple change the plugs or coils.

 

Anyway, will be taking lots of pictures.

 

Thanks again for all your advice.

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Good Morning,

 

I have attached some pictures of the coils from cylinders 3 and 5.  The coil from cylinder #5 looks a bit rough.  Will try swapping and see if misfire follows the coil.  Either way I guess I will need to find a source for some new coils.  Haven't pulled the plugs yet.  A visual inspection with a mirror did not indicate any obvious issues there.

 

Thanks for all your help
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Coil packs don't seem to be a big issue on Subarus but I've worked on many other vehicles where coils will begin to fail at 50k miles and you just have to replace them one at a time as they fail.

 

I would at least pull the #5 spark plug and see if it is fouled because of the misfire. Doesn't do you much good to put a new coil on a dead spark plug. If the plug is fouled and the others appear to be in good shape, you can replace just that one as a temporary measure. Just be sure to buy the same brand and type of plug. When you're reasonably assured that the problem has been fixed, replace the other plugs as well to avoid future running issues.

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Good Afternoon,



Pulled all of the coils.  #6 cylinder coil is also starting to come apart at the laminations.  The others aren't too bad so I will definitely replace #5 and #6.  I swapped #3 and #5 coil this morning and then ran the car a few miles.  Checked the code and the misfire had moved to #3 coil.   Photo attached of all the coils. 

AllCoilsOut


Also pulled the plug from #5 cylinder.  It looks okay to me but there again I am not a spark plug expert.  (photo also attached of the plug). 

Sparkplug#5Cyl

 

I did order a set of plugs along with the coils today.  For now I will try running it with the existing plugs.

 

Many thanks to grossgary and fairtax4me for your advice.  Will follow up again with a post once the new parts are in.



 

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Yes, the rust can weaken the magnetic field of the coil causing a weak spark.

The laminated cores make a big difference in determining the strength of the magnetic field.

There could also be rust intrusion into the coil windings causing a weak spark.

Where did you source the new coils?

 

Spark plug looks fine, but while you're in there...

Edited by Fairtax4me
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The coils are not available locally here from parts stores (Advance, AutoZone) nor from the local Subaru dealer.  Rock Auto had coils for $72 each versus $100 plus from parts stores/dealers.  Plugs are coming too so I can install them if I am feeling ambitious.  The coils were fairly easy to get out.  The plugs, on the other hand, will be a bit more work.  We'll see...

 

Hopefully this will correct the problem.  (For now! We live in "rust" country) :)

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  • 4 weeks later...

Well, I replaced 4 out of the 6 coils.  We have driven the car almost 2,000 miles since then, including a 1600 mile road trip, and it is running great.  We were getting something like 27 mpg through the mountains and some heavy traffic along with the usual summer construction stop and gos.  At some point I will replace the other two coils along with the plugs. Thanks again for all of your responses.  Hope this helps someone else as well.

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