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2010 Forester 2.5 X 4-speed Automatic
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Discussion Starter · #1 ·
Over two years ago I had a head gasket job done on my 2010 Forester because of a leak. The heads and the valves where sent out. I even had timing belt and water pump done even though the car only had 72,000 on it. The mechanic who did the job is a Subaru master mechanic who decided to close shop after a better less stressful job offer. I now take my Subi to a local dealership and they've treated me good but I'm a little concerned about a recent diagnosis. My check engine light came on twice within one month. The error code pointed to a miss in cylinder 4. After the first error they replaced plugs, cables, and ignition coil. After the second appointment the said I would need a valve job! There were no compression or leak down tests performed and I was told that's the only other cause they can think of. Friends tell me to get compression and leak down performed first. What else could it be? And was diagnosis a little premature? FYI I now have 92,000.
 

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MY05 Forester 2.5 XT 5MT
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3,165 Posts
Could be any of the following:

Piston Rings / Ringland Failure
Valve Train problems
Fuel Injector blocked up / failing
Wiring to fuel injector
Wiring to Coil/Sparkplug
HeadGasket Failure

What state were the plugs in when they were removed/changed? Any signs of oil etc ?
How is your mpg compared to before the problem showed up ?

You need a compression and a leak down test first before anything else - This is pretty fundamental stuff
Throwing parts at the problem until they get lucky is going to be really expensive otherwise :(
 

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2010 Forester 2.5 X 4-speed Automatic
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Discussion Starter · #4 ·
Thank you. Having compression and leak down test this Friday. I hope it points me in right direction. Wouldn't bad fuel injector code?
 

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MY05 Forester 2.5 XT 5MT
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The 09 onwards Forester went CANBUS from memory so it might throw up codes differently but when I had an 06 XT with a fuel injector out and bad wiring, I was only getting a misfire code on that cylinder, nothing else. It caused the MPG to drop through the floor too and gave horrific emissions.
From memory it was on Cylinder 2 or 4 too.

Post the results of the compression and leak down tests and we'll give you our 2 pence worth :)
Is the place that is doing the compression and leak down test able to give an emissions report with an exhaust probe on idle (When warm) and again at 2,000RPM and again at 3,000RPM Giving CO and HydroCarbon results by chance? (Much like emission testing is done in some areas) If it shows very rich or very lean burn, that could be a clue as to what is going on too.
 

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2010 Forester 2.5 X 4-speed Automatic
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Discussion Starter · #6 ·
It is a dealership so I'll assume they can but I will know for sure by tomorrow when I take her in for the tests. Will post results.
 

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2010 Forester 2.5 X 4-speed Automatic
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Discussion Starter · #7 ·
They could not do the emissions report you suggested but they did perform the compression and leak down test. The verdict was carbon buildup and a top down cleaning was performed. Cyl #1 87 @ 90 = 3% / Cyl #2 86 @ 90 = 4% / Cyl #3 83 @ 90 = 9% / Cyl #4 85 @ 90 = 6%. (Cyl #3 after cleaning 85 @ 90 = 6%). To put this in perspective, a $349.00 repair versus $2,200.00. Thanks Boys!
 
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