Author Topic: Misfire and Subaru has no clue what's wrong  (Read 1621 times)

March 07, 2016, 07:56 PM #0

leiflarsen Offline

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Last Tuesday night was that super cold night (-25). My 2009 2.5L Legacy wagon started running rough, then the CEL and cruise control light came on.

Towed the car to Subaru. They said the CEL threw a misfire in 3 and 4, and changed the plugs. No dice. Then they cleaned the PCV. Thought the problem was solved, but it started misfiring again.

They've tried to make the problem happen again for the last 4 days, and it hasn't misfired again. So they gave the car back to us, saying they couldn't replicate the problem, so there's nothing else they can do.

I'm wondering if I could rely on your knowledge to maybe give me some ideas. There is that famous thread on clubwrx.net that says to clean the MAF . . . so I'll try that . . . but don't know if I can trust this car anymore if this could happen at any time.

Thanks in advance for your thoughts.

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    Misfire and Subaru has no clue what's wrong
    « on: March 07, 2016, 07:56 PM »

    March 07, 2016, 09:27 PM #1

    Riley Offline

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    Coilpacks?

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    #keepingitstock

      March 07, 2016, 10:08 PM #2

      Igor Offline

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      Start with cleaning the maf and if that doesn't fix it maybe do a compression test.
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        March 07, 2016, 10:09 PM #3

        themikewoo Offline

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        When I had my Honda Civic I was going through an issue similar to yours. Ran some carb cleaner, turned out to be carbon deposits that was preventing some valves to closes all the way. I also replaced all the electrical components.

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          March 08, 2016, 07:32 AM #4

          leiflarsen Offline

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          Plan for today is MAF cleaner and Seafoam for built up carbon.

          I'm kind of annoyed Subaru didn't check the compression when they changed the plugs. It's a massive pain in the ass.
          Last Edit: March 08, 2016, 07:35 AM by leiflarsen

            March 08, 2016, 07:48 AM #5

            Igor Offline

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            Originally posted by leiflarsen
            Plan for today is MAF cleaner and Seafoam for built up carbon.

            I'm kind of annoyed Subaru didn't check the compression when they changed the plugs. It's a massive pain in the ass.

            Its not really something they do unless you request it. Here's hoping its just a dirty maf.
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              March 08, 2016, 08:10 AM #6

              Josia Offline

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              I just had a very similar problem with my GTI. Misfiring on cylinder 2 and 4. Replaced the coilpacks and spark plugs and now she runs great again.
              [Feb 22 17:00:55] Shaun:i hate chatbox

                March 08, 2016, 10:35 AM #7

                leiflarsen Offline

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                Drove it back to the dealership while it was misfiring. They think the EGR valve could be sticking open . . . which would explain why it is doing this while cool.

                He said it might be a cracked head, but with a misfire in 3 and 4, that would mean two cracked heads, which us unlikely . . . but would make me the unluckiest guy in the universe.

                They're also going to pressurize the coolant system overnight to see if that has any impact.

                Here's a video of the smoke from my pipes this morning.

                https://www.youtube.com/embed/z8M2ysPiiJU
                Last Edit: March 08, 2016, 10:38 AM by leiflarsen

                  March 08, 2016, 10:57 AM #8

                  Colby Offline

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                  Originally posted by leiflarsen

                  Here's a video of the smoke from my pipes this morning.

                  Did you put in any seafoam in it to cause the smoke? was it parked outside over night?
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                    March 08, 2016, 01:04 PM #9

                    Stone Offline

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                    My Subaru just did that a week ago and I found the coil pack was toast.

                    I was driving and all of a sudden the car starts running like crap. There was more vibration and noise than normal, and a flashing check engine light. I went home to check the code and there was a misfire in cylinder 1. I cleaned the maf sensor, checked for exhaust leaks in front of the cat, checked all vacuum lines and intake/intercooler hoses, regapped plugs, but nothing changed. I swapped the coil packs on the same side and then cylinder 3 started misfiring instead of 1.

                    $130 for one coil pack from Subaru

                      March 08, 2016, 01:21 PM #10

                      IanB Offline

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                      My brother's Legacy 2.5GT was having a misfire at idle, lugs and coilpacks checked out fine, ended up being a partially clogged fuel injector.  Pulled it and sprayed it down with carb cleaner, and it's been fine since.  Might explain the white smoke in the exhaust as well (unburnt fuel?).
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                        March 08, 2016, 01:31 PM #11

                        Cherka Offline

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                        To me that amount of smoke seems a little off. If you ran seafoam or some other type or engine cleaner I could see that but if not I would start by checking for signs of head gasket failure maybe? Check coolant for oil and vice versa. Easiest way to tell in oil is if it is a milky look. Like Igor said do a compression test, That would be the easier way to pin point if its mechanical problems like a head gasket or it is indeed something like a coil pack. But by the looks of your smoke id lean toward head gasket. Im not 100% confident on this but maybe a coolant compression test might be a good way to test too, but I dont know if having a closed thermostat would affect the accuracy of the test.

                          March 08, 2016, 05:08 PM #12

                          Tanner20 Offline

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                          Compression test won't show much actually, it would be better off doing a leak down test so you can actually pinpoint whats actually wrong (If its in the motor)

                            March 08, 2016, 08:34 PM #13

                            leiflarsen Offline

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                            Originally posted by Stone
                            My Subaru just did that a week ago and I found the coil pack was toast.

                            I was driving and all of a sudden the car starts running like crap. There was more vibration and noise than normal, and a flashing check engine light. I went home to check the code and there was a misfire in cylinder 1. I cleaned the maf sensor, checked for exhaust leaks in front of the cat, checked all vacuum lines and intake/intercooler hoses, regapped plugs, but nothing changed. I swapped the coil packs on the same side and then cylinder 3 started misfiring instead of 1.

                            $130 for one coil pack from Subaru

                            Subaru called to say they now think it's my aftermarket coil pack.

                            Fingers crossed a $130 part solves this madness.

                              March 12, 2016, 09:16 AM #14

                              Riley Offline

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                              Originally posted by Riley
                              Coilpacks?

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                              Originally posted by leiflarsen
                              Subaru called to say they now think it's my aftermarket coil pack.

                              Fingers crossed a $130 part solves this madness.

                              Sooooooo what'd I mention there?
                              #keepingitstock

                                March 15, 2016, 09:06 AM #15

                                leiflarsen Offline

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                                Originally posted by Riley
                                Sooooooo what'd I mention there?

                                Yep . . . you may have called it on the first comment . . . but that was last Tuesday, and I haven't heard from Subaru since . . . so maybe not.

                                I'm starting to wonder what is up.

                                  March 16, 2016, 09:26 AM #16

                                  Earthworm Offline

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                                  Fuel rails are tight?  Could they leak when it gets cold?  Raw fuel smell?

                                    March 19, 2016, 09:51 PM #17

                                    awd_ftw Offline

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                                    I know you did some diagnostics yourself, here is a link I used when I had a terrible misfire. http://forums.nasioc.com/forums/showthread.php?t=2318069

                                    Mine ended being a dry rot/cracked FPR hose to the manifold.

                                      March 24, 2016, 07:30 PM #18

                                      leiflarsen Offline

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                                      New coil, and after three days of driving, the problem is back.

                                      Of course it presents itself on Bad Thursday, when the shop probably isn't open again until Monday or Tuesday.

                                      Originally posted by awd_ftw
                                      I know you did some diagnostics yourself, here is a link I used when I had a terrible misfire. http://forums.nasioc.com/forums/showthread.php?t=2318069

                                      Mine ended being a dry rot/cracked FPR hose to the manifold.

                                      Thanks for the link. I'll check out as many of these as I can myself.

                                      UPDATE: I lifted the hood, and the #4 plug lead had fallen off the new coil. Fingers crossed that was the problem.
                                      Last Edit: March 24, 2016, 10:35 PM by leiflarsen

                                        March 28, 2016, 03:28 PM #19

                                        Winter Beater Offline

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                                        Originally posted by leiflarsen

                                        UPDATE: I lifted the hood, and the #4 plug lead had fallen off the new coil. Fingers crossed that was the problem.

                                        I'd say that would definitely cause a misfire...

                                          April 09, 2016, 01:46 PM #20

                                          Wagonman Offline

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                                          swap your injectors and see if the misfire follows, easy and free way to eliminate one potential source of the problem

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                                            Misfire and Subaru has no clue what's wrong
                                            « Reply #20 on: April 09, 2016, 01:46 PM »