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2004 forester
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Discussion Starter · #1 ·
My 2005 forester base model has a CEL light on. Error code PO302 cylinder 2 misfire detected. I am capable of most routine repairs. Auto zone clerk says changing coil and spark plug but I would appreciate any ones suggestions on diagnosing exactly what the problem is. Does each cylinder have it's own coil? If so is each coil the same link to best video for changing the coil I would probably do a complete tune up to start? Please advise thanks
 

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2001 Forester S, 4EAT
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Since your vehicle has individual coil packs. You can test my moving the coil pack from Cylinder 2 to one of the other cylinders and then seeing if the misfire moves with the coil pack. How many miles on the vehicle? Original copper plugs on the 2005 needed changing out after 30,000 to 40,000 miles. But if the existing plugs are NGK Iridium, then they should last nearly 100,000 miles
 

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+1 on relocating the coil pack to see if that gives you a different P030X code. I'd also pull the plug on that cylinder to check it's condition but that's just me. .....or just replace them while you're at it if it's time as mentioned.

EDIT: I forgot this is a 2005. My wife had a 2008 which had a coil and plug wires. If that's the case, check the connection to the coil, signs of wear on the plug wire and connection to the plug. I'd also pull the plug and you can still switch the wire with one of length close to it to see if the problem continues to another cylinder.

....but again, you may just want to change the wire if it's that time. .....along with the plugs if they are ready to be replaced as well.
 

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2004 forester
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Discussion Starter · #4 ·
@Kean The car was actually running rough at low end so the error code makes perfect sense. My question If I change the wire and plug on #2 and the vehicle runs fine then that kind of eliminates the coil? If not then good chance the coil is the problem yes? Thanks
 

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2007 Forester Sports XT 4EAT
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41,240 Posts
@smartin1019 is that 2005 an XT? If not, you have an Ignition Coil and Ignitor Assembly... a coil pack & not individual coil packs.

Note that member have had issues with aftermarket coil packs. Better to go with new factory/OEM or used.

Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]
 
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Possible, yes. ....assuming nothing is wrong with the plug, etc.

I once had a loose plug wire at the coil. Caused a misfire code but problems started when I rinsed the engine out and it took forever to start. I actually saw and heard the arc.

From the damage to the wire connection the the coil, it had been that way for a while but no other signs of a problem until then. Anyhow, replaced the wires and all was good.
 

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2004 forester
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Discussion Starter · #7 ·

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2004 forester
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Discussion Starter · #8 ·
Since your vehicle has individual coil packs. You can test my moving the coil pack from Cylinder 2 to one of the other cylinders and then seeing if the misfire moves with the coil pack. How many miles on the vehicle? Original copper plugs on the 2005 needed changing out after 30,000 to 40,000 miles. But if the existing plugs are NGK Iridium, then they should last nearly 100,000 miles
Car has 52,000 original miles Are you sure about the individual coil packs when I search for the parts it seems to indicate one main coil? In that case replacing the #2 coil pack and plug and wire should fix problem?
 

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2007 Forester Sports XT 4EAT
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2004 forester
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Discussion Starter · #10 ·
@2.5x_sleeper Very good link thanks. My plan to start is change #2 wire and plug and see how the car is running?

Not to get ahead of myself but the second reason for this problem is "clogged or faulty fuel injector" how the hell do you diagnose that? Change fuel injector?
 

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2007 Forester Sports XT 4EAT
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2016 & 2018 2.5i Premium CVT
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P030x is a general purpose code indicating a misfire in Cylinder x. Unfortunately it can run the gamut from plugs and their wires all the way up to injectors. Start at the bottom and work your way up.
 

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2004 forester
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Discussion Starter · #13 ·
@bbottomley Could you elaborate on the steps you would take? I will change the wire and plug first then probably the coil if still NG what next? ect. ect. Thanks
 

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2016 & 2018 2.5i Premium CVT
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That's as far as I've ever had o go. I've read posts about injectors but fortunately never encountered the situation.
 

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2005 Forester EJ251, 2011 Forester FB25
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If you search the net there are a number of posts about your model. I own one also. As far as I know, it is the 'wasted spark' type of ignition where both sides of the high tension coil go to a spark plug (ie there are only two HT coils all in the one pack). This means the opposite side plug or wire or the coil pack itself could be adding to the problem. On the basis that there are enough posts about this coil pack on the net, I carry a spare coil pack (purchased from a wereckers for $40 Australian) in the car all the time. It is only held in by two M6 bolts and the electrical plug. It's easier to change that first than pull out plugs and the plug leads from them that never seem to want to be removed (use silicon grease on the rubber when you put them back on.).
 

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Search all four of the P030x codes, as info is relevant across all four cylinders. I tried a search on simply P030, but it didn't work.
 

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2006 Forester 5-speed manual
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When I had this problem with my 2005 model it was the plug lead...

Twice. The replacement was the same. New leads fixed it, but the coil pack is probably recalcitrant as I have some stumbling at low revs.
 

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2015 Forester 2.5i Limited CVT
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I had this problem and it was the coil pack. Replaced it with a new Subaru oem and problem solved. I did use a multimeter to test. I also changed the wires.
 

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2000 Forester
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Car has 52,000 original miles Are you sure about the individual coil packs when I search for the parts it seems to indicate one main coil? In that case replacing the #2 coil pack and plug and wire should fix problem?
If you 52k miles on it and haven't changed the plugs yet, it's probably time to do all four while you're at it. Start with just that and see if the problem goes away. I'd say next likeliest cause would be a plug wire, with a bad coil being well down the list.
 
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