Question about Subaru Forester

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My 2002 forester started misfiring about 3 weeks ago and the check engine light came on. I only notice the misfire while idling. It seems to accelerate just fine. I took it to autozone, they told me cylinder 3 was misfiring. I put in fuel injector cleaner. This worked and the check engine light came on again and the check engine reader said cylinder 3 again. So I thought since the fuel injection cleaner work for a bit that it might be a fuel injector. So I changed that injector. ( I unplugged the battery to do this) When I turned it back on it worked for like 10 minutes than started misfiring again and the check engine light was now flashing instead of constant. So I changed all of the spark plugs. Again this worked for like 10-15 minutes than started misfiring. Then I changed the spark plug wires and it worked for like 25 minutes before misfiring again. I just bought a coil pack and will change it this weekend. Does this sound like the problem? Or do you have any other suggestions. I changed the valve cover gasket about a month ago because oil was leaking onto the spark plugs causing to misfire, but it this fixed that misfire issue. I would just take it to a subaru dealership, but the problem is I live about an hour away from the closest dealer and I don't want to drive the car that far while it is misfiring. If all else fails I will. I think they are the only ones that can plug in to determine why the flashing check engine light. Thanks so much, Jared

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  • jared_howlan May 25, 2011

    Cool thanks! I am new to this website. Can I keep this question open if the coil pack doesn't work? That way I can keep communicating the symptoms and you can offer other possible solutions.

    You mentioned to try engine cleaner if the coil pack doesn't fix it. Where do I apply this engine cleaner?

    Also, does the computer know to turn number 3 injector back on once I change the coil pack or do I need to get it reset by the dealer? Or will unhooking the battery work?

    Thanks again.

  • jared_howlan May 25, 2011

    Sorry I put this in the comment instead of reply.

    "Cool thanks! I am new to this website. Can I keep this question open if the coil pack doesn't work? That way I can keep communicating the symptoms and you can offer other possible solutions. You mentioned to try engine cleaner if the coil pack doesn't fix it. Where do I apply this engine cleaner? Also, does the computer know to turn number 3 injector back on once I change the coil pack or do I need to get it reset by the dealer? Or will unhooking the battery work? Thanks again."

  • jared_howlan May 25, 2011

    Cool thanks for the reply. I dont have a 6 cylinder or a turbo engine, but I assume this still applies. I will print this out and take it to someone who understands it.

    I would still like to know if I have to get the computer to reset so that injector 3 turns back on or if it does it by itself.

    Thanks agian!

  • jared_howlan May 25, 2011

    Oh wait... Sorry I didn't see you had two comments... Like I said I'm new to this website.


  • jared_howlan May 25, 2011

    Do you recommend doing this type of engine cleaning anyway? Or regularly?

  • jared_howlan Jun 17, 2011

    Soo I changed the coil pack... that didn't work. I brought the car to, what I thought to be a good mechanic, turns out he's reeeally slow to getting around the things. Anyways, he said the fuel injector still isn't working and this is the brand new one. So he put a new electrical wire on the wire that tells the fuel injector to work. For some reason he thought this would fix the problem. It didn't. So now he ordered a new computer that controls the fuel injectors. Do you think this would fix it?


  • jared_howlan Jun 23, 2011

    You're stumped as well huh? I don't think anybody knows how to fix my car.


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Hello first of all

I would be glad to give you the best advice as a mechanic for 8 years 3 for bmw and 5 with ford motor company.

That being said your diagnosis is good and you followed the correct troubleshooting guide lines so good job with that. I am not super familiar with subaru but if you have one coil for all cylinders this is most likely not your problem but a good way to check your coil is take the spark plug out of head , then reconnect to spark plug wire lay spark plug near a metal surface and have someone try to start the car look at the color of spark if its blue spark your coil is not the issue if orange spark coil is faulty not firing a hot enough spark to fully ignite gas vapor. '

So with all that some newer cars do have coils with a coil pick up built in this may be faulty to if applicable to your car if so the only way to know is for you to change the coil.

However if the coil does not fix your issue i would strongly lean on a crankshaft position sensor and or a camshaft position sensor as they tell the ecu when to fire spark and in what order to fire it and are more commonly known to be faulty before all else.

The crankshaft position sensor is located either under the harmonic balancer pulley or facing the pully were the belt is not if under pulley you will need to rent from autozone a harmonic balancer pully puller its free just pay and get money back when you return.

camshaft position sensor is normally located were the distributor was located easy to locate if diffident though.

If your coil does not resolve the issue one of these two will.

Please if it helps 4 thumbs and testomnial would be greatful for thanks any ? just ask

Posted on May 26, 2011

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Hi Jared, it sounds like your on the right track. This flashing Engine light is normal when you have a missfire thats constant and is bad enough to damage the cataylst. I think the coil is the culprit, based on the time it takes to start misfiring it could be that the computer is aware of a problem in the coil and is shutting down number 3 injector to keep from washing down the rings. I would replace that coil pack and retest. I would mention to keep in mind also that carbon build up on the back of the valves can cause this also, however it is usually more noticable when cold and on intial startup. If the coil dosen't fix it, try some top engine cleaner like seafoam.

Posted on May 25, 2011

  • MechxD
    MechxD May 25, 2011

    Service Bulliten from Subaru:


    If you encounter a Turbo or 6 Cylinder vehicle with a bank-specific misfire code and through normal diagnostics can not isolate the cause, check the operation of the Oil

    Control Valves (OCV) with your SSMIII. It is possible that one of the oil control valves for the Active Valve Control System (VVT) may be stuck open or closed.

    An easy way to determine if your misfire is caused by a faulty OCV is to monitor the camshaft advance angle with the SSMIII. At idle, cam advance value should be "0". If

    you find one cam advanced and the other to be at "0", the OCV for the bank that is advanced is probably stuck. An easy way to verify this is by swapping the oil control

    valves from one bank to the other. In most cases you will be able to see if the valve's piston is stuck when you compare it to a good one. In any event the swap test is very

    simple. If the misfire moves to the opposite bank you just verified the faulty part.

    The data below shows a faulty oil control valve (stuck open). This allows oil pressure past the oil control valve and into the cam rotor, advancing the cam at idle when it

    should be in a neutral position. If the OCV were stuck closed, you would see the OCV duty value increase without the resulting increase to the degrees of cam advance.

    Keep in mind that this is not the only fault that can cause bank specific misfire.


  • MechxD
    MechxD May 25, 2011

    I am here to help so let me know what you find out, and yes disconnecting battery should reset computer and injector kills. Top engine cleaner is feed through any vacuum source when engine is idle at a slow rate like an IV drip. They have a special canister you can pour engine cleaner into that has a hose most parts store carry them or can get them.


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