Subaru Outback Forums banner
  • Hey everyone! Enter your ride HERE to be a part of September's Outback of the Month Challenge!
1 - 11 of 11 Posts

·
Registered
2007 Outback 2.5i
Joined
·
16 Posts
Discussion Starter · #1 ·
I have a 2007 Outback 2.5i Basic manual trans that I recently purchased. Today I was heading up a hill at about 50 mph in 4th gear and the engine suddenly lurched a bit and lost quite a bit of power and the CEL immediately started flashing. I carry around my OBD II scanner in my car so I hooked it up and it shows "P0304 Misfire Cylinder 4." I then drove to the parts store, purchased a new set of plugs and wires and installed them. Upon doing this I discovered quite a bit of oil coating the plug and dripping out of the hole on banks 4, 3, and 1. I figured this oil had fouled the bank 4 plug and I just need to do valve cover gaskets so this stops happening. I did the plugs and wires, cleared the code, and fired it up but bank 4 continues to misfire even after driving it for a while. There's no way the oil has already fouled the plug, especially since I put plenty of electric grease on the plugs. I don't want to cause any engine damage but I also don't want to throw money at it unless I have good reason to believe it will fix the issue. Any ideas about what it could be? Or does anybody know of other things I may be able to test?
 

·
Registered
Joined
·
19,236 Posts
Just for starters . . .

When the first misfires appeared, and the car lost power, did the misfiring/loss of power continue afterwards as you drove to the store?

Brand of new plugs and new wires installed? (Some here suggest only NKG.)

The #4 plug is often the most difficult to replace. Are you sure it wasn't cross-threaded and was tightened properly?

Check around the valve covers and the intake manifold for a hose that might have been dislodged when replacing the plugs and wires. (E.g., the brake booster vacuum is off the #4 intake manifold runner.)

Others might have additional ideas . . .
 

·
Registered
2007 Outback 2.5i
Joined
·
16 Posts
Discussion Starter · #3 ·
Just for starters . . .

When the first misfires appeared, and the car lost power, did the misfiring/loss of power continue afterwards as you drove to the store?

Brand of new plugs and new wires installed? (Some here suggest only NKG.)

The #4 plug is often the most difficult to replace. Are you sure it wasn't cross-threaded and was tightened properly?

Check around the valve covers and the intake manifold for a hose that might have been dislodged when replacing the plugs and wires. (E.g., the brake booster vacuum is off the #4 intake manifold runner.)

Others might have additional ideas . . .
The misfiring has not stopped at all since it started, even after brand new plugs and wires. The plugs are the cheapest NGK plugs offered by CarQuest and they are iridium. The wires are manufactured by Prestolite. I am positive the plug is threaded and tightened properly because it threaded very easily and I tightened to spec. I have looked for a loose, disconnected, or cracked hose multiple times and found nothing. Tried disconnecting some and plugging the hole instead but it made no difference.
 

·
On the Super Mod Squad
2002 3.0 VDC Wag + 2018 2.5 Leg Ltd
Joined
·
27,047 Posts
saw you had a 2006 LGT,...what happened to that ?

I would chuck them wires,...subarus are particular to wires/ plugs.

NGK Iridium IX are fine though.



rockauto for comparison purposes has wires
$35 buys correct: NGK 55004 {#FX101} NGK Wire Set
 

·
Registered
2007 Outback 2.5i
Joined
·
16 Posts
Discussion Starter · #5 ·
saw you had a 2006 LGT,...what happened to that ?

I would chuck them wires,...subarus are particular to wires/ plugs.

NGK Iridium IX are fine though.



rockauto for comparison purposes has wires
$35 buys correct: NGK 55004 {#FX101} NGK Wire Set
My turbo failed and sucked up as much oil as it could and that was the end of it. I was young and dumb and probably could have maintained it a little better. I'll get better wires when I can but I'm really doubting that's the issue since there was no change with the different plugs and wires. What are the chances my coil is bad?
 

·
Registered
Joined
·
19,236 Posts
This is tough because the problem seems to be isolated to cylinder #4. While the spark plug tubes for other cylinders also had oil in them, apparently there are no recorded misfires there, as might be expected if the oil was messing with the HV. Also, with new plugs and, for the time being, new wires in the tubes that are not saturated with oil, the make of wires doesn't suggest the #4 misfires.

That said, if the new #4 wire might be suspect, it could be swapped with the #2 wire to see if the fault moves with it, which I somewhat doubt.

The 3-4 ignition coil could be arcing on the #4 side. With the wasted spark system, cylinder #3 would still function, but not #4. If the misfiring occurs at idle, perhaps try some fine water mist in the area of the coil at night and watch for a telltale arc or "snap".

The suddenness of the onset of misfiring might mean a mechanical issue. The injector might have failed/blocked, or, hopefully not, a valve might have broken or a guide dropped. Compression might be compromised in that cylinder.

One more thought: a skipped timing belt. What's the mileage on the 07, and the status of timing belt maintenance?
 

·
Registered
2007 Outback 2.5i
Joined
·
16 Posts
Discussion Starter · #7 ·
This is tough because the problem seems to be isolated to cylinder #4. While the spark plug tubes for other cylinders also had oil in them, apparently there are no recorded misfires there, as might be expected if the oil was messing with the HV. Also, with new plugs and, for the time being, new wires in the tubes that are not saturated with oil, the make of wires doesn't suggest the #4 misfires.

That said, if the new #4 wire might be suspect, it could be swapped with the #2 wire to see if the fault moves with it, which I somewhat doubt.

The 3-4 ignition coil could be arcing on the #4 side. With the wasted spark system, cylinder #3 would still function, but not #4. If the misfiring occurs at idle, perhaps try some fine water mist in the area of the coil at night and watch for a telltale arc or "snap".

The suddenness of the onset of misfiring might mean a mechanical issue. The injector might have failed/blocked, or, hopefully not, a valve might have broken or a guide dropped. Compression might be compromised in that cylinder.

One more thought: a skipped timing belt. What's the mileage on the 07, and the status of timing belt maintenance?
Good suggestions. I'll check for the arcing. The car has 159,000 miles and the belt was done by the previous (original) owner at 90,000. I'm hoping it's a simple electrical issue but I was also considering the injector.
 

·
On the Super Mod Squad
2002 3.0 VDC Wag + 2018 2.5 Leg Ltd
Joined
·
27,047 Posts
Good suggestions. I'll check for the arcing. The car has 159,000 miles and the belt was done by the previous (original) owner at 90,000. I'm hoping it's a simple electrical issue but I was also considering the injector.
if in the end you think you need a coil,

do not get a aftermarket off brand one, subaru coils last like forever,...and say "subaru" on them (in big letters on the front / top)..


but before there were like 3 - 4 straight junk brands out there,...like better to get a used one from a parts yard off a car just like yours as the OEM is so reliable.. and the junk ones do not do the job.

NGK just started making them available in the NGK label recently, (like very recently, have not read anything bad about them coils,...their products are great though...biggest spark plug company in the world, ...they could have been making the "subaru" label ones for all these years but I have never read that )

what does the current coil say on it in there now? ( a previous owner could have swapped a junk one on it).

______

and this is regular stuff here on this board. (swapping wires around, reseating plugs etc.

if you re-seat a NGK plug be sure to use anti-seize, a virgin NGK only gets screwed in the first time without it, anytime there after it needs some lube....
@traildogck would like me to insert a joke or three ).
 

·
Registered
2007 Outback 2.5i
Joined
·
16 Posts
Discussion Starter · #9 ·
Good suggestions. I'll check for the arcing. The car has 159,000 miles and the belt was done by the previous (original) owner at 90,000. I'm hoping it's a simple electrical issue but I was also considering the injector.
if in the end you think you need a coil,

do not get a aftermarket off brand one, subaru coils last like forever,...and say "subaru" on them (in big letters on the front / top)..


but before there were like 3 - 4 straight junk brands out there,...like better to get a used one from a parts yard off a car just like yours as the OEM is so reliable.. and the junk ones do not do the job.

NGK just started making them available in the NGK label recently, (like very recently, have not read anything bad about them coils,...their products are great though...biggest spark plug company in the world, ...they could have been making the "subaru" label ones for all these years but I have never read that )

what does the current coil say on it in there now? ( a previous owner could have swapped a junk one on it).

______

and this is regular stuff here on this board. (swapping wires around, reseating plugs etc.

if you re-seat a NGK plug be sure to use anti-seize, a virgin NGK only gets screwed in the first time without it, anytime there after it needs some lube....

@traildogck would like me to insert a joke or three ).
There's no arcing at the coil for sure but that doesn't mean it's not the issue still. It says SUBARU on the top of it and it appears to be original. I'll check around to see if I can find a Subaru coil that won't cause my wallet to implode.
 

·
On the Super Mod Squad
2002 3.0 VDC Wag + 2018 2.5 Leg Ltd
Joined
·
27,047 Posts

·
Registered
2007 Outback 2.5i
Joined
·
16 Posts
Discussion Starter · #11 ·
Update: Since it's peach harvest season and almost apple harvest season I have no time to do anything but farm. So I brought the car to my mechanic and they did the coil and it seems to be fine now. Hoping it is all set now but I will update again if there is any further issue.


Sent from my iPhone using Tapatalk
 
1 - 11 of 11 Posts
Top