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Discussion Starter · #1 ·
Ive been having an issue that Im stumped with, my CEL is on saying I have a misfire in cylinder 1. . I took it to my local shop who's worked on many of our cars and is a trusted guy. They pretty much had the car for a month slowly trying to trouble shoot it. Spark plugs have been replaced (Im thinking of replacing them again with ones from Subaru. Current plugs are NGK 3764), ignition coil for cylinder 1 has been replaced. I asked my mechanic if there's any difference taking it do the dealer, they'll likely just do the same things but have parts on hand. It has stalled a few times and my MPG dropped down to 20. Current mileage is around 147k and its a 2012. Research for looking up a cylinder misfire is almost as bad as looking up the common cold on WebMD, everything seems to have similar symptoms. Just strange to never have this problem before. Im open to suggestions if anyone has any ideas where to look
 

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Air, fuel, spark.

Did they check that the ignition coil on that cylinder is being triggered by the engine control module, that it's generating high voltage, that there's a good spark at the plug?

Did they check that the fuel injector is being triggered, that it seems to be working (clicking), and if not clear, perhaps swap it with another cylinder to see if the fault moves with it?

Did they check compression and/or leak down in cylinder $1?

If the only fault is the misfire in cylinder #1, the spark plugs, even if not the exact ones Subaru uses, can't be the likely cause as it's only in one cylinder and not the others.
 

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Discussion Starter · #4 ·
Thanks for the replies and reminders. The car has 147,000 miles and this is the second time the plugs have been changed. Im not exactly certain of the miles on the plugs but I changed them when it was time with the mileage. Im pretty good keeping on top of the maintenance.

The ignition coil is working correctly. The new ignition coil was swapped around with cylinder 2 and still had the result of a cylinder 1 misfire. The fuel injector for cylinder 1 was replaced and same result.

Compression checked to be ok. Head gasket test showed no leaks.

My mechanic is just as stumped. Hes going to check the fuel pressure over the weekend. Cam and crank shaft sensor was checked and looked normal.
 

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rubber timing belt replacement?

or timing belt KIT replacement.?
 

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Discussion Starter · #6 ·
Timing belt was already replaced, by the same shop. They said it didnt need to be replaced
 

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Timing belt was already replaced, by the same shop. They said it didnt need to be replaced
I ask about the belt vs. a whole kit as:

the rubber timing belt itself may outlast the idler / pulleys/ tensioner in there. (this is not the same situation as on other makes,...and I have had to discuss this with my friendly independent mechanics local to me).

subarus seize something in the timing components and can pop a brand new belt.


sometimes a misfire is the visible problem of a timing belt problem surfacing.
...and 147,000 miles is a whole lot of time on those idlers/ pulleys/ tensioner.

(the water pump can last forever though).

______

and some dealers,...but not all like to do quick rubber timing belt replacements ignoring the rest of the components on these cars. (so like even if the job is listed as done at the pre-programmed 105 months , 105,000 miles the diaster can still happen).
 

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Discussion Starter · #8 ·
Im pretty sure the kit was changed vs just the belt as a single component. I dont have the documents on hand to look it up but the shop that has been doing the work has been the same shop since day 1, besides issues that I had to bring it to the dealer for warranty jobs. But Im almost certain the KIT you're describing has been replaced when it was time to do the timing belt. Also, the car doesn't have any oil dripping, no puddles in the driveway.

In some research on this site, could the PCV valve be part of it?

To give some backstory of this car and I apologize if it seems like apart of it that I left out. Ive had my Cat converter replaced three times. Strange I know, the dealer was just as baffled. The first time it was replaced was with in the first year I had the car and that was fixed at Subaru. The second time my shop did it with Subaru parts, the final time it went back to Subaru. It seems to be working well so far, I put about 500 miles on it a week. A friend of mine recommended a complete fuel system cleaner (Cataclean)and Ive been using that every few months. I havent had any signs of the Cat trying to fail again. No loss of power, no bucking, no big mileage drop.
 

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why did they replace the cat 3x without diagnoising why the car needed a cat in the first place.

it is a sad practice but one dealers like to do though. (swap expensive cats. vs. finding the cheaper problem ...and this board is populated with stories,).


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how old is the PCV valve.? that is $18-$25, and is a wear part, it does not appear on the maint. schedules but should.

a bad PCV valve typically makes for minor hesitation, (I wonder if one is in awful shape it could make for a misife).

are you burning / loosing any oil (gone but not on the ground?)
 

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Hold on a minute...you say that the ECM is 'telling' you that there's a cylinder 1 misfire, but you never mentioned that it has symptoms of a cylinder 1 misfire, other than, it stalled, which would take more than one cylinder to be misfiring. Can you feel it misfiring? Is it possible that the ECM is getting an erroneous signal from a faulty cam or crank sensor?
 

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Discussion Starter · #11 ·
Subaru did do a diagnostic when they had it as did my shop, but they couldnt get any errors. The last two times it was replaced No CEL came on, no codes. I left it with Subaru for a few days so their techs can check it out. Things they recommend to do, change the front O2 Sensor, ignition coil, fuel injector.... Those where all replaced when I got it back from them, I did the O2 sensor, my shop did the rest. I can usually replace a quart of oil in a month. No smell of burning oil, no sputtering. I dont believe the PCV valve has been changed. Since its a cheap part Im happy do change it. When I get the car back Ill see what the condition of it is.

I can feel the misfire, it idles low and rough. The few times the code cleared, each time came back to be cylinder 1 misfire. My shop tested the cam and crank sensor with new sensors, they werent the issue. After I told my mechanic is stalled that was his first go to.
 

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Scanned through the posts and see that the coil and plugs were replaced... but were the wires replaced?
 

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Discussion Starter · #13 ·
The wire harness wasn't replaced but I'm 90% certain it was tested
 

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The wire harness wasn't replaced but I'm 90% certain it was tested
on the older maint. schedule I think plug wires were good for 60,000 miles or 60 months whatever came first,....so guess what time it is.?
 

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on the older maint. schedule I think plug wires were good for 60,000 miles or 60 months whatever came first,....so guess what time it is.?
Isn't it coil-on-plug? If so, then no high voltage plug wires. That's also why it might be good to verify whether or not that particular coil is being triggered and a good spark is being generated.

There could be a broken or frayed wire going to the #1 coil. It might have been intermittent some time back, leading to occasional misfires, and that could have damaged the previous cats. Now the problem is more permanent and significant, and is manifesting in noticeable misfire hesitation. Misfires caused by lack of spark lead to raw fuel exhausting into the cat. That will ruin the cat quickly. Just an idea . . . .
 

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Isn't it coil-on-plug? If so, then no high voltage plug wires. That's also why it might be good to verify whether or not that particular coil is being triggered and a good spark is being generated.

There could be a broken or frayed wire going to the #1 coil. It might have been intermittent some time back, leading to occasional misfires, and that could have damaged the previous cats. Now the problem is more permanent and significant, and is manifesting in noticeable misfire hesitation. Misfires caused by lack of spark lead to raw fuel exhausting into the cat. That will ruin the cat quickly. Just an idea . . . .

I think FB25B are coil on plug.

I was looking on that maint. schedule I posted to this thread and it did not have plug wires.
implying 2 things. 2010-12 EJ253 outback are coil on plug, or they went with some kind of miracle long life plug wires.


but after 147,000 miles, even with a coil on plug I would think one of those things could use a zip tie or a wire tie to stay on. (something done by Ez30D people with 200,000 mile coil on plug that are still working fine).
 

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FSM shows COP.

Yes, the zip tie addition after years is the type of issue that could cause the misfires. However, I understand that the #1 coil was replaced with new. If it was installed properly, then the zip tie syndrome doesn't apply.

Each coil has three (harness) wires; one is a ground, one is battery voltage, and the third goes to the ECM and is the trigger to generate the high voltage at the plug. I would imagine that with all the time the car has been on the examining table, the voltages, and triggering signals, and the efficacy of the spark at #1 have been checked, but who knows . . .

We're working third-hand as far as knowing exactly what has been done . . .
 

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just looking at rockauto, and they sell coil on plugs for 2010 outback EJ253. and no plug wires. :wink2:

Ej253 impreza of 2010 and 11 seem to retain the old type of plug and wire, and noticable old type metal intake

...before switching to the FB20 in 2012.
 

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I'm not clear on whether the misfire is always present and always evidenced by rough idling and being "felt". In other words, does the misfire CEL come on soon after the codes are cleared, and if so, how soon? Does the CEL flash at any time?

The ECM monitors "roughness" by cylinder. "roughness" is equated to misfiring. A single misfire/roughness event might show on the roughness monitor, but not instigate a misfire code. I think the code is set only after the roughness events meet specific criteria. I wonder if the shop monitored the roughness data to verify the cylinder #1 misfiring and under what conditions it appears.
 

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Discussion Starter · #20 ·
I haven't had the car since the end of June, it's hard for me to say how long the light has been on for the misfire. But last time I had it was a few days ago, the shop had it for a month but drove it locally and couldn't get the CEL with all the other light's to come on. When I took it back for the reason to get the CEL to come on I put 80 miles on it and the CEL came back. I know the disconnected the battery a few times, they tried to recreate the issue. The engine didn't get a chance to cycle enough for them.

I'm likely going to replace the PCV valve and spark plug 1 with a new plug. The car isn't in my possession at the moment, still in the shop.

When / if the CEL clears, it usually takes a day or so to come back. With all the same symptoms of rough low idle, low mpg (20). I appreciate all the help, I'm looking into what I can. I'm going to check the wiring when I get it back. It has always been cylinder 1. A mechanic friend mentioned a burnt cylinder valve or bad head gasket. I can't remember if he saw oil on the ignition coil or the plugs.

Would replacing the valve gaskets help?
 
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