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#4 Misfire


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05 LGT wagon, stock...bone stock

205k miles/5eat

 

Awhile back, I started getting cylinder 2&4 misfire codes and engine vibration. Dealer told my wife to get a new engine. Had compression/leak down checked and was found good (though I'm not sure I trust the work anymore). Anyways...

Replaced:

MAF (but none of the O2 sensors)

Spark plugs and coils

All injectors

 

Car ran good and did not vibrate after the injector replacement, but starting idling a little low and rough. Haven't thought much of it, just trying to get some miles on it. Well, about 10k miles later...got cylinder 4 misfire code again. So I had the spark plugs renewed with iridium 60k. No more code.

 

There is an intermittent clicking noise coming from that side of the engine (drivers side) when the car is warmed up and at idle. Doesn't do it cold. Also, when I'm just slowly crusing at 35mph in 5th and give it a whisper more throttle while keeping speed up a hill (1500rpm-1900rpm), it feels like one of the cylinders is misfiring. Probably #4. You can feel the vibes like a tire is wobbling. If I gas it more to kick into a lower gear, the engine is smooth.

 

Been reading up, manual says that the clicking sound is something wrong with the valves/springs/etc...but the noise is intermittent. It is pretty early in the diagnosis and I haven't swapped anything around to see if the problem follows because I want to get the error code again. But the threads are leading me to the Oil Flow Control Solenoid Valve, or its oil feed strainers/screens (OCV/AVCS in other threads). Is there somewhere else I should be looking? Thanks for any advice help in advance. Cheers.

 

 

 

**Update: 12/8/2017

Items tested and replaced (all OEM parts from local Subaru dealership or online parts wholesaler) with problem still persisting: When changing seals, all surfaces were throughly cleaned and seals installed dry - New turbo inlet hose, new turbo outlet gasket, new TMIC (due to a found leak when pressure tested up to 10psig), new Bypass Valve and seal, Throttle Body to Intake manifold orange seal, Intake to TGV orange "donut" seals. Throttle body was pretty clean...no substantial residue build up. All intake hoses have a clean oil film in them. The TMIC to Throttle body hose has a little puddle of oil in the dip before the TB.

Even after all of this was done, vacuum was tested at 18.5inHg vac in park @ idle with the needle evenly bouncing slightly above and below. Freezing temps now. When car is under boost a flashing CEL sometimes comes on. Sometimes it is short lived and clears leaving no steady CEL, other times when backing off the throttle it will leave a steady CEL with flashing CC. After this event...code read with internal code reader when back home still shows the P0304 #4 misfire.

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Burnt valves is my guess. Stock tune can/will cause that.

 

Decide what you want to do with car...keep it for years or sell it.

 

Have you replaced the black o-rings between the intake manifold and TGV's with the new larger orange one's ? Those will cause issues when its colder outside.

305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD).  CHECK your oil, these cars use it.

 

Engine Build - Click Here

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I don’t have digits for the compression test. Only told that it passed. But yes, might be the best place for a redo by a Subaru specialist, non-stealership, just to get a second check on the engine life.

 

The intake gaskets are orange. Saw that from hosing down that side of the engine with contact cleaner, looking for engine surge from an air leak. In doing that, also saw oil coming from where the TMIC hose boots onto the EGR valve? before the intake manifold. I sprayed that down as well and saw it’s gasket is orange with no engine surge.

 

As for keeping the car, I am starting to look around...but would love to keep it if it only took $1k to fix this issue.

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I comment about keeping it, is more geared towards a rebuild. If you can do some of the work yourself, for about 4000 you can have a good running car for many years.

305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD).  CHECK your oil, these cars use it.

 

Engine Build - Click Here

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Well, I think the problem might not be a problem anymore. Found several places on intake air lines that had oil around the edges. Removed the intercooler and the hose to the throttle body was moving freely. Also saw oil around the edges of the tube going to the turbo intake. Got a new gasket from turbo to intercooler, tightened up air line to turbo hose clamp, and also the hose to throttle body clamp. As soon as I started her cold she seemed to instantly rev up quicker. Took her out for a test once warm and don't feel the wobbly jerky at the rpm speed range mentioned before. Hopefully that's it, but plan on putting all new intake gaskets and hoses on the next chance I get. Thanks for the help, it is much appreciated.
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Cobb AP V3 is what most do, go stage 1. Lot's of us go stage 2 with a 3" down pipe and then a custom tune. One of the best Tuners is tuningalliance@gmail.com If your serious about making the car run better, after all the small things are taken care of, reach out to Mike and see what he can do for you. He sometimes offers the Cobb AP and an e-tune for it.

 

He's kept both my cars happy for years.

305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD).  CHECK your oil, these cars use it.

 

Engine Build - Click Here

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Yes, stage 1 is for a stock car. Performance wise, its how the car should have come from the factory.

 

Someone else can comment on the O2 levels.

305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD).  CHECK your oil, these cars use it.

 

Engine Build - Click Here

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  • 3 weeks later...
Installed new intake gaskets, throttle body gasket, turbo inlet hose, turbo outlet gasket, and BPV gasket. (Major PITA). The weird thing is that when I took the BPV off the TMIC there was a little condensation on the bottom of the valve. Also never got to pressure test the TMIC, suspecting a leak since there is a little oil on the bottom of the fins closest to the turbo inlet.
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A smoked valve can give good compression readings, mine had good compression results but I had two burnt valves on #4. If the CEL is going away after you have fixed these air leaks then you just might have fixed the issue. Definitely get off that stock tune for sure. Maybe check out that PCV tube as well, mine was full of this butter looking substance @ 163K.
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No butter...just good looking oil inside. Oil changes every 4000 miles. Little to no oil consumption. Was also able to check out the turbo with the inlet hose off and zero play. I heard that if there is a powdery butter looking substance then that’s bad bad news.

The engine still slightly wobbles between 1500-1900 rpm uphill. Plan on checking the TMIC, cleaning the AVCS oil valves and screens, and replacing the O2 sensor. It has my full attention now.

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Bit newer to the stuff, and not tryimg to highjack the thread but at what mileage do a lot of cars go with the stock tune? I heading to 136,000 miles and she just stsrted yapping about her coil so I replaced that and the plugs. Also wong where one may find the PCV valve at? Again, relatively new to diy but trying to learn.
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No butter...just good looking oil inside. Oil changes every 4000 miles. Little to no oil consumption. Was also able to check out the turbo with the inlet hose off and zero play. I heard that if there is a powdery butter looking substance then that’s bad bad news.

The engine still slightly wobbles between 1500-1900 rpm uphill. Plan on checking the TMIC, cleaning the AVCS oil valves and screens, and replacing the O2 sensor. It has my full attention now.

 

That "wobble" is probably the notorious "stumble" that every Subaru I've seen has. There are several threads about it here.

 

Bit newer to the stuff, and not tryimg to highjack the thread but at what mileage do a lot of cars go with the stock tune? I heading to 136,000 miles and she just stsrted yapping about her coil so I replaced that and the plugs. Also wong where one may find the PCV valve at? Again, relatively new to diy but trying to learn.

 

There isn't really a PCV valve, just a tube that pulls pressure out of the crankcase (no one way valve like typical setups). Some cars go 200k on the stock tune, some only lasted 90k. Depends on how it was driven.

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Pressure tested the TMIC, checked the AVCS oil valve and oil supply banjo filter today. The TMIC does have a slight leak at the bottom turbo inlet corner at 10psig. Also, when I pressure tested it I was expecting the BPV to not let air through but there was air coming from the outlet under pressure. Is this normal? I can see a bore at the valve inlet that looks like it goes up to the top of the actuator (kind of like a backup means of actuating the valve) but am unsure. Need to dive into that more and see how it does what it does.

The drivers side AVCS oil feed banjo filter was nonexistent. Pulled that OCV out to see if the filter was lodged and was nowhere to be found.

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Another interesting point, is when the intercooler was pressure tested, it was at 70degF in the shop. The soap method showed no leaks. As soon as it was dunked in 51degF water to look for any bubbles...the leak was found.
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There isn't really a PCV valve, just a tube that pulls pressure out of the crankcase (no one way valve like typical setups).

 

The one-way PCV valve, which prevents the turbocharger from pushing air into the crankcase under boost, is located under the intercooler, in a hose that connects to the top rear of the crankcase just passenger-side of center.

 

Without that one-way valve, the turbocharger would create Negative Crankcase Ventilation and blow out the oil seals.

 

The un-valved sections of the crankcase ventilation system pull crankcase gases via the valve covers into the turbo inlet, which never sees boost.

 

The following diagram describes the operation of the entire PCV sytem, and also the operation of the PCV valve itself.

1497288311_PCVRouting.jpg.8cc1b13ca547dc7b3f9219f07b6fef10.jpg

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Cool info, but I was more curious about the bypass valve...and what makes it actuate. Testing the intercooler up to 10psig was causing air to exit the BPV outlet. I couldn’t find a detailed drawing of it anywhere that included the internal bore at the inlet.
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Cool info, but I was more curious about the bypass valve...and what makes it actuate. Testing the intercooler up to 10psig was causing air to exit the BPV outlet. I couldn’t find a detailed drawing of it anywhere that included the internal bore at the inlet.

 

Vacuum from the intake manifold, via the small hose, opens the valve and allows pressure coming out of the intercooler to flow into the turbo inlet. A small amount of leakage is normal, since the valve is plastic with no rubber seal. If you have substantial leakage, try opening and cleaning the sealing surfaces of the valve, then consider replacing it.

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Ok, finally found a cutaway showing the internal bore but can’t get it to upload. It looks like the bore goes to the bottom of the diaphragm. So the bypass valve works more off a differential pressure across the Throttle body.

 

Here’s a link to the pic http://subaruidiots.com/subaru-turbocharger-explained-part-1/subaruturbocharger6/

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Still waiting on the intercooler to show up. Ordered through a Subaru parts wholesaler out of Bellevue WA. The car still starts up great with no rough idle. As soon as I put it into drive, it bogs down a touch and idles a bit more rough. Still “wobbly” feeling between 1500-1900 rpm. Need to comb through the manual and create a checklist of items...though most seem to say “rough idle” as a symptom. No wonder why this problem is such a PITA.
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