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2022 Outback Touring XT, 2020 Outback Touring XT and 05 Outback 3.0R
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Discussion Starter · #1 ·
I have an 05 Outback 3.0R and my check engine is on. I scanned it and it showing me that misfiring detected cylinder 3 & 4. The current mileage is at 108k and the spark plugs are original. The mechanic told me I need to replace the spark plugs and the ignition coils. Is there a way to test if the coils are bad? I've read somewhere that these coils are bullet proof. Also, what are the locations of cylinder 3 & 4?

Thank you,
Tin
 

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On the Super Mod Squad
2002 3.0 VDC Wag + 2018 2.5 Leg Ltd
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27,113 Posts
subaru estimated the original NGK plugs should have been changed every 60,000 miles under normal operation conditions, so you are almost 2x that.

Subaru maintenance schedules and new car break-in period- 2000 through 2009, links for 2010, 2011...

suggestion: replace the plugs with NGK,...and then consider the coils. some people here have had to lock the coils down with a zip tie or a bread tie, as the clamp on them has gotten a little bad from being worked at plug change time
...but other then that rare is anyone out changing coils on a H6 car,... and given good service and fluid changes these can go 400,000 miles.

alternatively as you got a problem on both sides of the engine, you might also have a bad engine ground,
(although I would think there would possibly be more cylinders ???)

here is a schematic to show you where the plugs are by number:

 

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The failure rate is low on those coils, but it isn't zero either.

For the math nerds: My car has 3 out of 4 original coils at 183k miles.

It is definitely time for new plugs, NGK ILFR6B for that one.
 

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2022 Outback Touring XT, 2020 Outback Touring XT and 05 Outback 3.0R
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Discussion Starter · #4 ·
Thank you guys. Can I use LFR6AIX-11? My local auto parts don't have the original spark plugs.
 

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On the Super Mod Squad
2002 3.0 VDC Wag + 2018 2.5 Leg Ltd
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Thank you guys. Can I use LFR6AIX-11? My local auto parts don't have the original spark plugs.

some people here use the IX over the laser Iridium in their EZ30R series cars. (maybe a difference in change interval).

NGK only lists the laser iridium ILFR68 or SILFR688 as the right one. PartCat

Rockauto lists only the ones you list LFR6AIX11 (Iridium IX) for $5.96 each plus $6 mail to give you a idea if the local parts store is screwing you. (I get their things like next day in the mail as their warehouse is only 100 miles away form me for typical things like plugs,...even though rock auto thinks its 4 days).


I did not try amazon as a cost comparison (they maybe cheaper then rockauto, I would only buy such things from amazon prime though to ensure they come as specified and not,...never shipped from a grocery store trying to sell auto parts ...which really happened to me once on spark plugs, I successfully canceled my order)..
 
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