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2004 Subaru OBW L.L. Bean H6. 2003 Subaru OBW L.L. Bean Former 2001 Subaru OBW VDC owner.
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987 Posts
Discussion Starter #1 (Edited)
I wonder if a consensus could form to say what symptoms are specific to a failed coil vs a failed injector when coupled with only a PO306 code.
Many forum members have encountered the PO306.
Who replaced an injector to fix the issue? Who replaced a coil to fix the issue? what exactly did your car do before you fixed it?

I get a blinking check engine light when I’m at idle, but when I drive at any speed I don’t get the check engine light at all, (after I’ve cleared it with an OBD tool). I have actually caught the engine light just starting to blink, but as soon as I stepped on the gas it would go away before the solid check engine light could come on. It’s like acceleration controls what the ECM was about to alert me to with the check engine light.
I feel the slight rocking/vibration of the engine at idle, but have full power through all driving speeds. Initially, Sometimes at idle I would have no vibration or symptoms at all....,but now it’s all the time.
This JDM engine has been sometimes wet/damp while sitting for the 5 years it sat before its recent installation. I reckon it has around 60k on it and all its components.
This engine has been driven 200 miles with a bottle of gum out. MPG seems bad, but I’ve been running the heat. I estimate I’ll probably get 300 miles on a full tank. The first 150 miles since the installation of this JDM, I’ve had rough idle, but no check engine light until now, and I’m at about the 200 mile mark since installation.
 

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Outback 2011 3.6R Premium
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791 Posts
I would suspect the problem you are having is an injector that is only "dribbling" at idle which is causing your "misfire" condition.

If it is dribbling at idle it is probably not running properly at higher revs, maybe resulting in the engine being slightly under powered.

The easy way to tell if it is an injector, spark plug or coil would be to swap the coil/spark plug to a different location. If the misfire moves with the coil/spark plug then you know that is the problem.

Seagrass
 

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2004 Subaru OBW L.L. Bean H6. 2003 Subaru OBW L.L. Bean Former 2001 Subaru OBW VDC owner.
Joined
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987 Posts
Discussion Starter #3
I would suspect the problem you are having is an injector that is only "dribbling" at idle which is causing your "misfire" condition.

If it is dribbling at idle it is probably not running properly at higher revs, maybe resulting in the engine being slightly under powered.

The easy way to tell if it is an injector, spark plug or coil would be to swap the coil/spark plug to a different location. If the misfire moves with the coil/spark plug then you know that is the problem.

Seagrass
Thanks seagrass. You know I think I'm going to go for it. I'm going to change out the injector. I'll go to the dealer and get all new seals for some of my extras laying around, that way I'll be sure to have no leaks. Thanks again for the confirmation.
 

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Outbacks, SVXs, XT6, 4Runner, Celica, Brat, E150s
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I agree it sounds like that injector isn't closing and that I would swap that injector with an adjacent one.

If you've got a parts engine there, then the injector is easier than the coil. OE injector seals are EXPENSIVE. Go aftermarket.
 

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2004 Subaru OBW L.L. Bean H6. 2003 Subaru OBW L.L. Bean Former 2001 Subaru OBW VDC owner.
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987 Posts
Discussion Starter #5
I agree it sounds like that injector isn't closing and that I would swap that injector with an adjacent one.

If you've got a parts engine there, then the injector is easier than the coil. OE injector seals are EXPENSIVE. Go aftermarket.
ive got injectors from my last two outbacks with 180k and 210k miles. I guess I have like 12 of them. If the seals look ok I’ll pick the best one. I’m assuming I can pull the rail and replace the o rings on the tops of the three of them, and only have to pull out the whole injector in cylinder 6.
They’ve been in my tool box in the garage for 3 to 5 years or so.
 

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2004 Subaru OBW L.L. Bean H6. 2003 Subaru OBW L.L. Bean Former 2001 Subaru OBW VDC owner.
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987 Posts
Discussion Starter #6
@cardoc @eagleeye @CNY_Dave
I am moving this chat over to this thread I started.

I went to the junkyard today to do a test run of the procedure of removing a fuel injector before going at it with my car.
I've learned you should never worry about too much difficulty removing the bolts from the injector cover, because nothing I own, or ever will own, could be as rusty as the one in the junkyard, and those came out fine no problem.

I worried about my PCV hose breaking, but the one on the JDM engine in the 03 Bean slipped off with ease.

I replaced my coil, the one furthest back by the steering wheel where the PO306 code is being thrown, with a brand new OEM coil, and I checked the plug. See the pic. The plug is brand spanking new. I now remember replacing all of them on the JDM a long time ago. Also, it's very easy to get that difficult back coil AND spark plug from the top after you remove the battery and washer fluid reservoir.

TIPS I can share with the forum are:
1. Keep an eye on the upper O-rings when you pull off the rail. If they go flying it'll drive you nuts thinking they might be stuck up in the rail, or if you've already pulled out an injector you might worry one of them flew down in the big injector hole, which could turn into a nightmare. Don't pull any injectors out until you have the rail off and you know where the upper O-Rings are.

2. Before even starting the job of replacing injectors go and buy 6 O-Rings, so I've been told already. Pay the ridiculous money for them and don't ask questions. If you have money to burn go ahead and replace all the grommets too, but mine all looked good with no tears, so I'm not going to replace those.

Be advised, I'm only working on the driver's side of my engine, and I'm not worrying about the other side right now. I don't have any problems over there now, so it's not a concern. I'm just working on and talking about the 3 injectors on the driver's side of the engine.
I will say, my O-Rings did not look or feel bad, but I'm not messing around with gasoline seeping out on a hot engine. I'll be replacing all six O-Rings on the 3 injectors on the driver's side of the engine I've been fiddling with.

3. Prepare to spend moola on the O-rings. Dealer wants $6 and change, Advanced auto wants to only sell you a whole kit for each injector at $16 and change a pop, and NAPA wants $5 and change for I think two O-rings. Pay the money.

4. @Brucey thanks for this tip. You don't have to start the car to see if you have a leak, just turn your key on and off a few times. When you turn the key on you are also shutting on the fuel pump which will send fuel to your fuel rail. Work on a cold engine. Be CAREFUL, you don't cause spark moving your battery in and out, especially if you've spilled gas. Dangerous stuff folks, please be cautious here.

5. Be prepared for a outlet of pressure when you first pull off the fuel rail. Gasoline might even spurt, so wear goggles. Have some rags down to sop up the gas.

So I got my injector replaced and slapped the fuel rail back on, but had a leak coming from the middle injector when I turned my key on. I just decided to stop right there and call it quits for the day. I'll be picking up all new O-rings tomorrow or this week and will finish the job later. Back to driving the 04 Bean for now.

Before pulling off the fuel rail I did have a chance to start the car and see if the check engine light still came on after replacing the coil and checking the plug, and it did. So the plug and coil can be ruled out for causing the check engine light and PO306 code. Also, the plug was bone dry, and so was the coil. The plug was in there tight and right.
 

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2004 Subaru OBW L.L. Bean H6. 2003 Subaru OBW L.L. Bean Former 2001 Subaru OBW VDC owner.
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987 Posts
Discussion Starter #7
Could mass flow sensor, a bad power steering pump, or EGR valve cause a PO306 code?
 

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2003 OB-H6 VDC
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66 Posts
We don't have mass airflow or EGR on these engines. And a power steering pump would not cause this issue. Put a noid light on the plug for injector 6 and see what the light looks like at idle versus higher rpm's. Could be a bad ground or other resistance issue causing you lose voltage at that injector.
 

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@Lverano

Bit of a long shot, but have you monitored the Rear O2 Sensor voltage to see if it's working properly? (This is the O2 sensor after the rear cat converter.) There's been cases, albeit with more recent 2.5s, where a bad rear O2 sensor caused odd misfire symptoms at idle that disappeared when off idle.
 

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2004 Subaru OBW L.L. Bean H6. 2003 Subaru OBW L.L. Bean Former 2001 Subaru OBW VDC owner.
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987 Posts
Discussion Starter #10
@Lverano

Bit of a long shot, but have you monitored the Rear O2 Sensor voltage to see if it's working properly? (This is the O2 sensor after the rear cat converter.) There's been cases, albeit with more recent 2.5s, where a bad rear O2 sensor caused odd misfire symptoms at idle that disappeared when off idle.
Thanks, I've not been to the site for a while. I'm game for anything at this point. I feel that could for sure be possible if you say so. I've yet to reinstall my injectors and flip them around to see what's what. My next shot is going to be cleaning up all the grounds. This car sat garaged for a few years, and the engine sat longer, like 5 or 6. I'd not be surprised if the grounds cleaned up would fix it.

Interestingly enough you know you shook my memory a little. I think way back when I had originally taken the exhaust off of this 03 Bean I might of had trouble with the rear O2 sensor, and broke it taking it out. I think then I might of put an O2 sensor from the 01 VDC in there... I don't remember though. It'll be something to check down the line if the injector and ground trouble shoots fail to correct the issue.
 
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