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Registered
2009 Forester XT
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11 Posts
Discussion Starter #1 (Edited)
Yes, there is a lot already written about this code, and it's probably one of the worst you can get. People of said their turbos blew not long after this showed up, but luckily I've driven a thousand miles without any serious problems....

2009 XT Limited
I bought the car in August of 2018 after two months of searching Craigslist and LetGo. I met the seller, who turned out to be an used car dealer, who bought the car after a dealer could not sell it (a VIN search on Google showed it was offered for $10k six months earlier). The interior was super clean and so was the engine compartment. I took it for a test drive and boosted it a little, but was I was pretty sure the car was in good shape. I got a good deal, or so I thought.

I've learned a lot from these forums and so I hope I can help someone by sharing my experiences.
 

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2009 Forester XT
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11 Posts
Discussion Starter #2
I know something about cars, after doing a SR20DET swap on my 240sx, but I'm an armchair mechanic and new to Subarus. The CEL light came on shortly after I got the car home, and using a $6 bluetooth scanner and the Torque app, found the P0011 code. Searching the forums, I found several recommended Subaru repair shops in the NYC area. My nephew recommended his shop in NJ, so I took a calculated chance to drive the 30 miles, hoping the turbo would not blow along the way.

The shop took out the AVCS solenoid, tested it, and said it was fine. Since we didn't know the oil change history on the car, their recommendation was to do two oil changes in the next 500 miles with good synthetic oil, and to use premium gas (doh!). Synthetic oil has better detergent properties and it would help clean the engine. For a good measure, I put 1/4 can of Seafoam into the crankcase. A few hundred miles later, I changed the oil myself and could not believe how dirty the engine was (it was only 500 miles since the last oil change).

The CEL would still come back after resetting it. The engine had hesitation problems, and going WOT, boost would mysteriously cut off. I cleaned the MAF, replaced the air filter, used a bottle of spray Seafoam on the throttle body, replaced the PCV valve (which turned out to be OK), replaced the spark plugs with Autolite Double Platiums (yes they do work). I found oil on the old spark plugs which made me wonder whether or not I was getting good spark and about bad gaskets around the plug wells.

I was starting to make a laundry list of things to check and replace. Turbo shaft play, compression test, leak down test, replace coils and wires, gas filter, gas pressure regulator, etc. All this stuff was going to cost a lot of money, and there's no guarantee that any of this was going to fix my problems. So the best thing to do was to the cheap repairs first....
 

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Registered
2009 Forester XT
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11 Posts
Discussion Starter #3
Fix #1
The engine hesitation and boost loss was caused by a bad air bypass valve. I was lucky to see the CEL come on while the turbo made a fluttering sound when I quickly let off the boost. The Subaru OEM BOV was $100, but I got it for $75 at Subaru Parts Superstore. For a piece of plastic and a vacuum diaphragm, this was pretty expensive considering that bought a Porsche/Audi BOV for $25 for my SR20DET.

The engine definitely drove better, but I still experience occasional hesitation at low speeds and RPMs. I somehow got the idea that perhaps the transmission was not downshifting properly, and was ready to do a tranny drain and fill when I came across another P0011 post.
 

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Registered
2009 Forester XT
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11 Posts
Discussion Starter #4 (Edited)
Fix #2
Replace the AVCS solenoid. Although the mechanic told me it was fine, I read posts from other owners who claimed that cleaning the AVCS helped, but they eventually replaced them and their CEL never came back. Looking on eBay, I found a few sellers offering solenoids for $20 shipped. "What could I lose?" or so I figured. I ordered one and tested it using a 9v battery. I could not see any movement for the life of me, so I wondered if these most-likely-made-in-china solenoids could be any good, and maybe I could damage my engine.

I asked my local NY mechanic what he thought (he didn't like me using Autolite plugs and suggested that I only use genuine Subaru tranny fluid). He gave me the thumbs up, so I took a chance thinking I can pull the eBay part if the CEL light would immediately come on. And it didn't :)
 

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2009 Forester XT
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11 Posts
Discussion Starter #5
Current Status
After 150 miles, I am happy to report that the CEL has not come back on. The engine is sounding much better, as if it was a Honda VTEC. My engine hesitation is gone, and it boosts well. Although I think it still has some flat spots, an AccessPort might do this trick. I bought some Valvoline MaxLife tranny fluid, but I'll wait another 1000 miles before I introduce another variable.

The engine oil still looks good, unlike the synthetic oil, after the same miles driven. I'm going to guess that the Seafoam and first synthetic oil change helped flush out the engine.

Looking over my car, it looks like the previous owner was not so lucky trying to sort out the check engine light. The gas cap and fuel filler neck looks new, and the rear seat was missing some plastic pieces - perhaps lost when they replaced the in-tank gas filter. I wish the first mechanic had simply replaced the AVCS solenoid when he pulled it out (and remembered to put the valve cover hose back on), but I doubt if anyone would think a $20 part would cause this much trouble and anxiety for two months.
 

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2011 Forester
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10 Posts
Thank you for posting this! It inspired me to replace the AVCS solenoid, even though it worked when I tested it with a 9V battery. I just drove about 40 miles and P0011 did not come back! It idles normally again. It might be a bit too early to celebrate, but based on how the car was acting before, I'm fairly confident (fingers crossed) that it was the solenoid. Thanks again!
 

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2004 Forester XT 4EAT
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1,291 Posts
Good job on diagnosing.

I'd still suggest NGK's, too, but your car(ll). :)
 
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