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2008 Outback Limited 2.5L 4AT (EJ253)
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Discussion Starter #1
2008 Outback Limited 2.5i

Bought the car used at 152.5K in March 2018, it idled rough and stuttered coming to a stop but there were no check engine lights, I figure (and my mechanic) it's probably misfiring because of a bad spark plug. No 100k service done, and seemingly infrequent oil changes by last owner. My mechanic does a whole list of service, I'll list the estimate, then the actual work performed.

Estimate: Head gasket (my request, because.), head bolt set, subaru coolant, water pump gasket, thermostat(includes gasket), camshaft seal, timing belt component kit with water pump, crank seal, valve cover gasket set, NGK laser platinum spark plugs, Duralast wire set, engine oil(5W30), oil filter (M4615), Cylinder Head Gasket labor Total:3005.76 (He checked the screen in the assembly when he he replaced the solenoid and switch and it was CLEAN)

Actual: everything plus Air Filter, Radiator Cap (7037), Oil Switch (25240AA060), Oil Valve (VVL)(10921AA040)(He checked the screen in the assembly when he he replaced the solenoid and switch and it was CLEAN) Total 3161.73

After service (like immediately after I picked it up) it throws P0026, variable valve lift solenoid or pressure switch and then wont accelerate past 4k RPM, well they were just both replaced but my mechanic rechecks them, and spends 7 hours checking all the connections back to the ECM and finds nothing wrong. No charge, but he wont work on the problem anymore. Rough idle still present, stutter during stopping still present.

I had a diagnostic done at my local Subaru dealer ($108) and I don't know what they actually did but their findings were:
LCA Codes P0026 Oil Solenoid Valve and Code P0420 Catalytic Converter below threshold. Recommend removing valve cover for further diag & replace Cat Conv. 153615 Tested Oil Solenoid & Oil Solenoid Switch & both are operating normally. Need to remove right side valve cover to inspect cylinder head & determine source of oil restriction causing low oil pressure limiting proper valve function. Minimum labor charge $540 for cylinder head investigation, $850 for Cat replacement.

Well I picked up the Cat for 600 right away but havent put it in yet. (this CAT was part of a recall campaign, last one from that batch, newer ones are $1300+tax) So I have that just sitting around until we can solve the misfire/P0026 code. I tried clearing the code and seeing when it comes back on, and it's during driving when the RPMs hit 4k, when the solenoid should be sent into "high" mode.

I switched to premium gas and put in a seafoam cleaner, as well as a few oz into the oil, and that actually caused a marked improvement in the rough idle, but the misfire still feels present and the stuttering at stops is still there too, undiminished. I just picked up a PCV valve and in going to replace that I noticed that the air intake chamber had a port broken off and siliconed back on so I'm going to wait and replace them at the same time (had to order from denver) on friday 4/27/18. I also plan on having the fuel injectors replaced if it's a reasonable price.

If I can't figure this problem out by Monday 4/30/18 I'll have to let Subaru start digging into the bank 1 cylinder head to see what they find, the estimate is between $540 (taking apart cleaning and putting back together) and $2100 (replacing entire cylinder head and a couple attached bits).

Does anybody have any suggestions for me!? I can call Subaru tomorrow to see if they have any info on what they did during diagnosis, so let me know what to ask about. I plan to ask them to do any additional tests you can think of before proceeding with the tear down.
I can do a lot at home, but I have no idea what else to check! Could my mechanic have done something wrong during the timing belt/head gasket job?
Why wont this P0026 code go away!
current mileage 154K

Oh yeah, add in $145 for the map light unit to get rid of the airbag light! unrelated to the current problem though.

All in All I'm in like $9612 with this car so far and I want to make sure that number doesn't go up another 2k if possible.

PLEASE HELP!
my phone number is 240 271 2643, if you have any questions/comments feel free to contact me directly for a faster response.
 

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2008 Subaru Tribeca
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890 Posts
Were the OSV pressure switches actually replaced?
 

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2005 OBXT Limited, VF37, STI intake, 5MT
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1,553 Posts
I would grab a cheap OBD2-to-USB cable and start data logging with RomRaider and/or FreeSSM to see what the ECU is seeing. Watching the actual values can help eliminate many hours of diag time and point to a cause. FreeSSM may also be able to cycle the solenoid to check for operation while the engine is running.

My suspicion is that there is an issue with that bank alone. Either it be a plugged passage to the oil pressure sensor, low oil pressure to the solenoid, stuck rocker arms, etc.

Personally, I think the rough idle, failed cats and P0026 is leading to a stuck AVLS rocker or two in Bank 1. The system is only "working" below ~4K RPMs (low load, idle, cruise) to help promote good swirl patterns. If these are "stuck" open at low RPM, they could cause issues like this. The older VTEC systems in some D16 Honda's would do something similar. They'd suck above 4500 because the VTEC system wasn't working and the extra valves wouldn't open.

I'd put low system pressure near the end of my diag path as usually low system pressure results in a P0028 AND P0026 (both banks).
 

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2008 Outback Limited 2.5L 4AT (EJ253)
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Discussion Starter #5 (Edited)
I would grab a cheap OBD2-to-USB cable and start data logging with RomRaider and/or FreeSSM to see what the ECU is seeing. Watching the actual values can help eliminate many hours of diag time and point to a cause. FreeSSM may also be able to cycle the solenoid to check for operation while the engine is running.

My suspicion is that there is an issue with that bank alone. Either it be a plugged passage to the oil pressure sensor, low oil pressure to the solenoid, stuck rocker arms, etc.
I have a cheapo USB/OBII cable but no laptop at the moment (actually one is in the mail) so i'll have to wait to try that.

If it is a blocked oil passage to the switch how would I address that?

What would low oil pressure to the solenoid mean?

If it is a stuck rocker arm how would that be addressed?

I'm going to call subaru and see if they observed the state of the solenoid during driving or not to see if the ECM signaled correctly and or if the solenoid functioned at high RPMs.

I reset the code this morning and it came back at idle this time.
 

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2005 OBXT Limited, VF37, STI intake, 5MT
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If it is a blocked oil passage to the switch how would I address that?
One could remove the solenoid and pressure switch and blow air through the passage to emulate/check operation of the AVLS system. If it's found to be blocked, a chemical bath is usually easiest (blast it with some brake cleaner), but a tube cleaner might be possible, if the passages are straight enough.

What would low oil pressure to the solenoid mean?
Low feed pressure could be do to bearing clearances out-of spec on the camshaft, blocked passage in the oil galley, or a leak at the oil feed to the cylinder head.

If it is a stuck rocker arm how would that be addressed?
Removing the rocker cover (valve cover) would provide decent access to the rocker arms. Rotating the engine by hand (or cranking with ECU disabled) would allow someone to watch the action of the rocker arms to ensure they are operating correctly.

I'm going to call subaru and see if they observed the state of the solenoid during driving or not to see if the ECM signaled correctly and or if the solenoid functioned at high RPMs.

I reset the code this morning and it came back at idle this time.
You might have to contact the tech directly, but IMO, it's doubtful. The official diag process (in the FSM) only calls for circuit diagnosis for that particular code. Experienced techs will probably think/look outside the box for this code, but that's luck-of-the-draw when dropping off at the dealer.
 
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