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Strange EJ251 Misfire

EJ251 5M Outback Misfire Help Maintenance

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12 replies to this topic

#1 ayykimber

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Posted 25 September 2017 - 10:03 AM

Hello all, 

 

My 2002 Outback has developed a very strange misfire recently, and while it probably inst a Subaru specific issue (I don't think at least), I wanted to ask y'all for help since y'all haven't done me wrong yet.

 

The misfire started last week, it wasn't too bad at first, but got progressively worse and worse up to the point where it was feeling down on power, and stuttering to the point where it would almost stall out when moving away from a light. There was and still is no check engine light, it stuttered like crazy moving off from a standstill, it backfired like crazy, and it developed a small tapping noise that sounds like either an injector, something else top end, or even a small exhaust leak when I was moving/accelerating. I started running through the procedures of figuring out what the issue was, and I had narrowed it down to bad gasoline since I had filled up from a station that ran its tanks dry and had their pumps sitting for a few days. I threw a can of Sea Foam into the tank later in the week in the hopes that it would help fix any weirdness in the fuel. It did help, so over this past weekend I refilled from about half a tank and drove 300 miles round trip to my hometown and back to run out the tank and squeeze out any junk in there. While I was in town I pulled the spark plugs on the passenger side as well as the injectors. They were acceptably clean upon visual inspection, so that sealed the deal for me that it was a fuel issue (I didnt get a chance to flow test the injectors since I didn't really have the time/money to see if they were up to snuff however.) I also checked the plug wires and there were no breaks in them, they haven't been shorting on anything, and the contacts looked clean.

 

When I returned back to town I refilled from very nearly empty, and drove it around town a bit. It was a night and day improvement, it didn't stutter anywhere nearly as bad, (the coupled of times it did stutter it was quickly killed off by adding more gas when moving away from a light), and even the tapping noise had either gone away or had quieted down to the point that I couldn't hear it. So, I thought everything was fine and dandy, I went ahead and poured another can of Sea Foam into the tank to stabilize any bad fuel left in the system, and called it a day. 

 

However this morning when I got in to drive to class, the stutter and tap had returned in force. What was interesting about this round is that it subsided quite a bit once the motor got some heat in it, and the noise was either very quiet or non existent. There still isn't a check engine light either. I'm pretty thoroughly stumped by this. I'm good with a wrench, but I cant diagnose to save my life so any help will be greatly appreciated. 

 

Just a little background on the car to make things easier (hopefully), it has 177k miles on it, it has had head gaskets done in the last 20k miles, O2 sensors replaced in the last 5k miles, and I just put a new catalytic converter on it less than 1K miles ago. It's also had the fuel filter replaced at some point, although I have no idea when. This thing has seen a pretty hard life, so honestly anything on this thing breaking wouldnt surprise me at this point.

 

Thank you all in advance,

 

-A


Edited by ayykimber, 25 September 2017 - 10:08 AM.


#2 1 Lucky Texan

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Posted 25 September 2017 - 10:58 AM

the 2 things that come to mind first are; moisture on bad plug wires or the coil, or oil on the plug boots. Early morning dew/moisture can cause arcing/misfiring that goes away when engine heat drys the high voltage system. Some folks have used a plant 'mister' with water to look for the issue - while idling after warming up, spray the mister around unti the car begins stumbling. Doing this at night can sometimes allow you you see arcing.

 

If there was oil on the wire boots, you need new valve cover gaskets.

 

given that there may be a bad fuel issue, fuel filter may need changing now.

 

you might scan the ECU even without a CEL on. There may be pending codes.

 

One more idea, older soobs often have bad/cracked knock sensors. They are cheap and easy to replace and may not throw a code.

 

you might try a search on the above issues and see if others have had success with similar symptoms.



#3 ayykimber

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Posted 25 September 2017 - 11:32 AM

the 2 things that come to mind first are; moisture on bad plug wires or the coil, or oil on the plug boots. Early morning dew/moisture can cause arcing/misfiring that goes away when engine heat drys the high voltage system. Some folks have used a plant 'mister' with water to look for the issue - while idling after warming up, spray the mister around unti the car begins stumbling. Doing this at night can sometimes allow you you see arcing.

 

If there was oil on the wire boots, you need new valve cover gaskets.

 

given that there may be a bad fuel issue, fuel filter may need changing now.

 

you might scan the ECU even without a CEL on. There may be pending codes.

 

One more idea, older soobs often have bad/cracked knock sensors. They are cheap and easy to replace and may not throw a code.

 

you might try a search on the above issues and see if others have had success with similar symptoms.

 

I do know that the plug wires and the valve cover gasket were replaced along with the head gaskets, it is unlikely that that is the case, and I didnt note any breaks in the wire when I was checking it out. However, I will give them a check because I did notice a bit of oily/watery residue on part of the lead that go into the head to contact the plug (what ever that's called) of the number one cylinder when I pulled it so there may be something there and Im not gonna rule anything out considering what I've seen on this thing. Just spray water around the plug wires and where they go into the head, and see if anything happens? 

 

I was also thinking fuel filter this morning when I was driving in so that my be my next step, Ill also see if I can get my hands on a scanner next time I'm home to look for codes and see what the idle mix is doing. 

 

I've also never heard about the knock sensor issue on these cars, I'll look into that as well. Where would it be located and what will I be looking for?

 

Most other threads I've looked into says it's an O2 Sensor, but since they were replaced so recently I'm somewhat doubtful that it's faulty. Best explanation I can come up with that one is that one of em didnt get plugged back in quite properly when I did the cat, but I would imagine that the fault would have popped up earlier since that was done about a month ago. 

 

Thanks for your help!

 

-A


Edited by ayykimber, 25 September 2017 - 11:44 AM.


#4 1 Lucky Texan

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Posted 25 September 2017 - 01:07 PM

you can search for KS threads here and there are several youtube videos.



#5 ayykimber

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Posted 25 September 2017 - 01:54 PM

you can search for KS threads here and there are several youtube videos.

 

 

Thanks, Ill give those a look too!

 

-A



#6 Fairtax4me

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Posted 28 September 2017 - 08:14 AM

Tapping sound? Sounds like a plug wire or the coil is arcing.
Wait until it's dark out and spray some water on coil and plug wires and look for arcing.

#7 ayykimber

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Posted 28 September 2017 - 08:53 AM

Tapping sound? Sounds like a plug wire or the coil is arcing.
Wait until it's dark out and spray some water on coil and plug wires and look for arcing.

 

I'll give that a look as well. 

 

Also just a quick update on the situation, the stuttering has been pretty minimal to non existent in the mornings lately, which is strange considering the mornings in the area have been pretty cool and pretty wet from all the humidity and condensation. This morning for example it was about 50-60 degrees, humid as all get out, and the car was covered in condensation from the 96% humidity yesterday. However, it didn't stutter once on the way to work this morning. I didn't run with my windows down, but from what I could hear through the firewall the tapping was either gone or quiet enough that the noise wasn't making it inside. The afternoons have been the worst, exhibiting the symptoms I've described before, but it doesn't last quite as long as it used to. 

 

Current plan of action is checking out the coil and plug wires, and doing a visual inspection of the knock sensor since that's the best I can really do in terms of that with the tools I have at my disposal. If they look fine/don't arc, I'll just put some miles on it and see where that gets me. For better or worse.

 

-A


Edited by ayykimber, 28 September 2017 - 09:01 AM.


#8 idosubaru

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Posted 28 September 2017 - 09:04 AM

Does the check engine light work?

I would read the codes and see if any are pending

Timing belt and pulleys ever been replaced?

Is the knocking piston slap or not?

#9 ayykimber

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Posted 28 September 2017 - 09:29 AM

Does the check engine light work?

I would read the codes and see if any are pending

Timing belt and pulleys ever been replaced?

Is the knocking piston slap or not?

 

The Check Engine Light definitely works. I just got the bugger to go away after replacing the catalytic converter and both O2 sensors. The timing belt and pulleys were done when we did head gaskets a few years ago. 

 

It shouldn't be piston slap, since the tap is pretty recent, there haven't been any signs of it up until like two weeks ago, and its a phenomena that does come and go no matter the temp it is outside, the water or oil temp, or the load on the engine.  It also sounds very much like top end noise, the best I can describe it is an extremely noisy injector. Volume doesn't really get louder with revs, but the tapping does get faster.

 

-A



#10 1 Lucky Texan

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Posted 28 September 2017 - 09:35 AM

doesn't seem like rod knock. also, doesn't seem like a weak TB tensioner but, I wouldn't ignore that possibility.

 

 

you may want to skip ahead

 

https://youtu.be/tAxiFJ2rHBE


Edited by 1 Lucky Texan, 28 September 2017 - 09:36 AM.


#11 ayykimber

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Posted 28 September 2017 - 09:39 AM

doesn't seem like rod knock. also, doesn't seem like a weak TB tensioner but, I wouldn't ignore that possibility.

 

 

you may want to skip ahead

 

https://youtu.be/tAxiFJ2rHBE

 

The noise at 5:33 is definitely not what I am hearing. But that at least rules out one possibility.

 

Thanks

 

-A



#12 ayykimber

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Posted 28 September 2017 - 03:07 PM

Hey all,

 

I managed to get some audio of the stutter on my way home from class today. It's faint since I literally just started recording with my phone my dash cubby, so you will need earphones or something with goo bass range to hear it. It is there however, especially towards the end around 1:15, 1:30, and 2:45.  Also I am aware of the squeaking at the beginning, my clutch throw-out bearing wasn't broken in properly so it squeaks like crazy and my power steering pump is going (I have a pump on my shelf waiting to go on, and I plan to do that in November so expect a thread on that here in a month or so.)

 

I haven't been able to get good audio of the tapping yet. You can catch it in the video posted below with your speakers or earbuds on max and the bass removed, but it is very very faint and barely heard even with your speakers all the way up. It's best heard at low revs when moving, so I may try again later tonight to get audio of it. Hopefully it will be a smaller file this time so I can just upload it straight to here rather than going the long way around like this time.

 

Hope this helps!

 

-A

 

https://youtu.be/6EGD7Eki3w8


Edited by ayykimber, 28 September 2017 - 03:25 PM.


#13 ayykimber

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Posted 30 September 2017 - 08:38 PM

Hey all,

 

Just wanted to do a quick update. I drove the car home this afternoon and left it with my stepfather since he has access to all the diagnostic tools out there, so he can have a look and weigh in on things. 

 

On the way there the CEL came on, I had it scanned at the nearest Autozone off the interstate and the code was P0172-Mixture too rich bank 1. Is it safe to assume the coil and plug leads need to be replaced at this point, or is there something else we can consider now with this code?

 

Thank you all so much again for your help! Ill keep posting if we find anything else. 

 

-A







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