Misfire in Cylinder 4

[SaskyGT]

First time working on an engine with AVCS, and have searched quite a bit and couldn't find my scenario.

 

Bought a 2010 Legacy GT USDM with a very bad misfire on cylinder 4. Got it home, installed btSsm and started looking at the AVCS information. The intake AVCS seems good, reading the same and at 0* at idle.

 

The exhaust AVCS is wonky. The right side is 8* at idle, left side at 0*. While driving around the block the right side is moving up to a max of 18*, but the left side is stuck at 0*-2*. Current is present and duty cycle seemed to be stuck on 9.64% through the 1st gear drive around the block. Tonight, I will do a proper log.

 

Additionally, there are P0016 and P0017 as stored codes, but haven't come back that I can tell. I know there are better logs I can take, but the ultimate question I have is: can a malfunctioning right side cause a misfire in cylinder 4? Can a malfunctioning AVCS system on the exhaust side cause a misfire in general?

 

My steps for diagnosis were going to be:

1) swap OCV between right and left - cleaning them out while they're out

2) compression test cylinder 4

3) leak down test cylinder 4 if no compression (are there marks to indicate TDC cylinder 4 without taking off timing cover?)

4) depending on leak down test, check timing marks

5) ???

6) profit

[NVAKeith]

I don’t know squat about AVCS...I assume the low hanging fruit of swapping plug and coil was already done? Our coils are known to rust and fail in the salt belt.

[SaskyGT]

Man didn't even think of that. I just got it and threw a logger on and got some information. This car has lived its life in Ontario, Alberta, and now Saskatchewan.

 

I'll do a proper log (I forgot to record speed to indicate if I was idling or driving last time) then swap the coils around.

 

Thanks!

[dgoodhue]

Check the coils, it is common for the coil heat sink to expand from rust and the coil to fail in area where salt is applied to the roads.

[cww516]

Those left and right AVCS angles should match- I haven't had to do any work involving the oil control valves (OCV, if you were to search on here), but I've seen a couple of posts on here where people have had issues with them. Dunno if that would cause as bad of a miss as you're seeing, but it's certainly not ideal.

 

Coils are definitely a good thing to look at, though. A little surface rust is okay, but if the layers are peeling apart, that's no bueno.

[stewdogg]

1) swap OCV between right and left - cleaning them out while they're out

6) profit

 

1)I think the OCV's are side dependent. There is a tiny filter in each control valve that's removable, if you're very careful. Mine were filled with metal shavings from my beat up engine. One of my filters was ripped and needed to be replaced, but the other was salvageable. You can't get a replacement filter and have to buy the whole Oil Control Valve.

 

6) How can I get in on some of this profit?

[A_A_ron]

Cylinder 4 is the cylinder on the rear drivers side closest to you when you are driving the car. If you are having significant misfire on this cylinder it's probably because it got cooked. There's a guy in my town who has a 2010 LGT and when he took it apart cylinder 4 was toast.

 

Unless it's a coil pack I would assume it's the standard EJ problem. Do a leak test and you'll know for sure if your short block is shot.

 

Given the two error codes you listed and the fact your AVCs is showing different on right vs left you might have a cam position sensor issue or messed up timing.

[dgoodhue]

I got a P0017 code when I did my timing belt because was off by a tooth one of the cams. If I reset it, the engine check engine light would go away for a little while. Someone could have done a timing belt and put both driver side cams off by tooth. I didn't log the AVCS though as I knew pretty quickly it was my fault, because I had just done the timing belt.

[SaskyGT]

Thank you all for the help!

 

6) How can I get in on some of this profit?

 

We just need to understand step 5!

 

 

 

Did a drive, got a proper log that I will post later, but the gist is that the left exhaust cam is stuck between 0* - 4* and the right is 10*+ at idle, so something is wrong there, but from what I'm reading, the AVCS alone can't cause this issue.

 

Took off the coil packs for #2 and #4. #2 was an aftermarket coil and #4 was original. There was slight delamination of the shims on #4, but when switched #2 and #4, #4 kept the misfire.

 

Took the plugs out and nothing to note there.

 

Did a compression test on #4, 0 psi. This is where I had to call it a night.

 

Today, the plan is to remove the timing covers and take a look at the marks, if all is in time, get #4 TDC and do the leak down test. Either way, engine is going to have to come out unless it is timing that can cause just #4 fail.

 

If it is the short block, the 5th gen LGT seems to be an unique assembly, but if I understand correctly, the cylinder block is only different because of an extra hole for the oil pan. The other differences are the front engine mount and the water pump is different on this engine. It seems the 2010 LGT short block was AB980 which is now replaced by AC860. For all other cars, 2006-2014, it was the AB630 which is now replaced by the AC880. Is the only difference between the AC860 and AC880 the bolt hole for the oil pan? An AC880 seems to be much easier to acquire due to covering many more years of vehicles.

 

With that in mind, can I grab any turbo'ed EJ25 or does it have to be an EJ255 v2 short block? From what I read, does the below sound right for moving parts of the current block over to the "new" one:

• swap oil pan (goop over the missing hole)
  
• new 2010 LGT water pump
  
• swap heads
  
• swap accessories (AC, power steering, alt)
  
• swap both manifolds, including throttle body
  

[SaskyGT]

Unless it's a coil pack I would assume it's the standard EJ problem.

 

Can this be rebuilt in this case and this a common thing for cylinder #4 to be fried?

[A_A_ron]

Did a compression test on #4, 0 psi. This is where I had to call it a night.

 

It's fried. Yes but it's a little pricey. You can send off the block to a few different Subaru shops around the country and they can re-sleeve it. You other option is to find a used EJ25 and pop it in. You probably only need a short block if your heads aren't toast but given the cam issues it might be safe to get a long block.

 

IAG puts together EJ motors all day long and they will go right in great but you are paying a premium for upgraded parts and the brand new block.

 

 

Read this entire thread. The early posts are doubtful but the more you read the more they start to understand why the mod was made.

https://forums.nasioc.com/forums/showthread.php?t=2882734

The EJ has fundamental flaw with how the coolant flows through the left hand head and some say the knock sensor location exacerbates this. If you find pictures of blown EJs you'll notice a trend that cylinder 4 is the one the is messed up or looks the worst.

 

IAG short block. This will be bullet proof unless you go big turbo.

https://www.iagperformance.com/IAG-Stage-1-2-5L-Subaru-Short-Block-WRX-STI-LGT-p/iag-eng-1002.htm

[A_A_ron]

Can this be rebuilt in this case and this a common thing for cylinder #4 to be fried?

 

https://forums.nasioc.com/forums/showthread.php?t=2821336

 

Yes, it is very common. Even though the ringland piston design was improved at some point I believe the issues still lies with the over heated cylinder.

[FLlegacy]

Our engine also comes with the larger oil pump found on the STI engines, apparently the dual avcs calls for more oil volume. So be sure you are also getting the correct pump.

 

Burnt valves are more common on our engines than a standard ej25 ringland failure. This issues has popped up at least a few times in our forum, so don't write off that engine just yet, until you have done the leak-down test.

 

For what it will cost to have the engine rebuilt you would be better off buying a built short block and installing that. Otherwise the most cost effective option would be to order the correct short block from Subaru directly, IMO.

 

If it were me I would at least consider a used engine, this version of the ej25 has not been problematic like those used in previous WRX and STI models I think there have been a couple of knocking issues documented on here but nothing like has been documented on the previous gens. You also need to consider the extra oil scavenging pump on the passenger side head that will not be included in a standard STI or WRX long block assembly, and if your short block is toast I would be hesitant to reuse the heads without them being properly cleaned and rebuilt. Do it right the first time for sure.

Edited October 4, 2019 by FLlegacy

[SaskyGT]

Our engine also comes with the larger oil pump found on the STI engines, apparently the dual avcs calls for more oil volume. So be sure you are also getting the correct pump.

I'm not familiar with these engines too much, can the pump from my current block be switched over to another EJ25 block?

 

Burnt valves are more common on our engines than a standard ej25 ringland failure. This issues has popped up at least a few times in our forum, so don't write off that engine just yet, until you have done the leak-down test.

Any tips for finding TDC on #4? I'm used to the 4G63 and just putting a straw in the cylinder hole, but with a horizontal cylinder, not sure how well that will work. If it is a burnt valve, the motor will need to come out to get the head off, correct?

 

You also need to consider the extra oil scavenging pump on the passenger side head that will not be included in a standard STI or WRX long block assembly, and if your short block is toast I would be hesitant to reuse the heads without them being properly cleaned and rebuilt. Do it right the first time for sure.

Getting the heads redone shouldn't be too bad, but might not be able to get it done locally is the only concern. Up in Canada, stuff can be pretty far away sometimes. If I get any EJ25 longblock, keep: the heads, oil pump, oil pan, and water pump (replace)?

 

This isn't a car that I was going to go all out on, I have a 2g DSM that is more than enough. I was thinking of a few simple things to make it breathe a bit better and doesn't have to work as hard. The number one thing I'm after for this car is reliability, which it seems that using aftermarket bearings and better specs for the clearances can help with, but I need a machine shop in Canada for that.

 

What I can't seem to get a good grip on is all the variations of engines that Subaru has. An EJ255 isn't the same as another EJ255 because it uses different heads and block. Is there anywhere that spells out what blocks and heads are used on different vehicles and model years and what the differences are? There is a guy selling a brand new 10103AC890, but I can't seem to find if it is an EJ255 or EJ257 - it is used only on Impreza WRX and STI from 2008 to 2014. Would it be worth to grab it or order the exact short block code from SOA?

 

I won't get a chance to do the leak down until Saturday, so I'll hold off speculating too much, but I do like learning and there is certainly lots to learn about the different engines, but also a lack of exact information.

[FLlegacy]

I'm not familiar with these engines too much, can the pump from my current block be switched over to another EJ25 block?

 

 

 

 

 

Any tips for finding TDC on #4? I'm used to the 4G63 and just putting a straw in the cylinder hole, but with a horizontal cylinder, not sure how well that will work. If it is a burnt valve, the motor will need to come out to get the head off, correct?

 

 

 

 

 

Getting the heads redone shouldn't be too bad, but might not be able to get it done locally is the only concern. Up in Canada, stuff can be pretty far away sometimes. If I get any EJ25 longblock, keep: the heads, oil pump, oil pan, and water pump (replace)?

 

 

 

This isn't a car that I was going to go all out on, I have a 2g DSM that is more than enough. I was thinking of a few simple things to make it breathe a bit better and doesn't have to work as hard. The number one thing I'm after for this car is reliability, which it seems that using aftermarket bearings and better specs for the clearances can help with, but I need a machine shop in Canada for that.

 

 

 

What I can't seem to get a good grip on is all the variations of engines that Subaru has. An EJ255 isn't the same as another EJ255 because it uses different heads and block. Is there anywhere that spells out what blocks and heads are used on different vehicles and model years and what the differences are? There is a guy selling a brand new 10103AC890, but I can't seem to find if it is an EJ255 or EJ257 - it is used only on Impreza WRX and STI from 2008 to 2014. Would it be worth to grab it or order the exact short block code from SOA?

 

 

 

I won't get a chance to do the leak down until Saturday, so I'll hold off speculating too much, but I do like learning and there is certainly lots to learn about the different engines, but also a lack of exact information.

The block is identical across the wrx and sti line, the pistons are different as well as some minor upgrades on the ej257. Our block is only different in that it has the provision to mount our oil pan and adapter. The ej257 has a slightly lower compression and slightly better pistons.

 

The real differences are the heads. Wrx is almost all single avcs, where STI and our cars are dual avcs. Our car is the only ej255 to use the larger oil pump as well, it comes standard on the ej257.

 

To find tdc on cylinder 4, I would remove the valve cover, set the engine to zero timing mark, then turn it over 4 times. That should be tdc of #4. You can verify the valves are closed by looking at the cam position.

Edited October 4, 2019 by FLlegacy

[SaskyGT]

The block is identical across the wrx and sti line, the pistons are different as well as some minor upgrades on the ej257. Our block is only different in that it has the provision to mount our oil pan and adapter. The ej257 has a slightly lower compression and slightly better pistons.

What adapter are you referring to?

 

The real differences are the heads. Wrx is almost all single avcs, where STI and our cars are dual avcs. Our car is the only ej255 to use the larger oil pump as well, it comes standard on the ej257.

So an STI longblock (swap oil pan, water pump, grab the passenger side scavenger pump) would be acceptable?

 

Are there any major differences with a non-turbo EJ25 short block? I'm assuming there is, but figured I would ask. When I'm looking at wreckers and etc... I will for sure want a turbo'ed EJ25?

[FLlegacy]

What adapter are you referring to?

 

 

So an STI longblock (swap oil pan, water pump, grab the passenger side scavenger pump) would be acceptable?

 

Are there any major differences with a non-turbo EJ25 short block? I'm assuming there is, but figured I would ask. When I'm looking at wreckers and etc... I will for sure want a turbo'ed EJ25?

The oil pan adapter skirt thing. Non turbo engines are a non starter for us. Most are single cam, open deck.

 

Sent from my SM-G965U using Tapatalk

[SaskyGT]

Okay, so the weekend didn't go as planned, but here we are. Got the timing covers off and found the timing belt in abhorrent condition.

 

Also discovered the timing is off by a tooth. Please let me know if I'm missing something, but every other rotation when the crank marks were aligned, the exhaust cam is off.

Can a tooth off cause zero compression or will there still possibly be compression?

 

Didn't have the time to pull the valve cover or figure out when the valves are closed for the leakdown test.

 

Hopefully tomorrow will get that done if the kids cooperate.

 

Speaking of possible replacement options, there is a wrecked 2004 outback xt vin: 4S4BP67C054338355 coming up in salvage auction starting at $800. 347,000 km though! Written off for damage to the side, not front end collision. Thoughts or just too much mileage? No history to say if it ever has had the engine replaced.[ATTACH]279828[/ATTACH][ATTACH]279829[/ATTACH][ATTACH]279830[/ATTACH]

Edited October 7, 2019 by SaskyGT

[dgoodhue]

Okay, so the weekend didn't go as planned, but here we are. Got the timing covers off and found the timing belt in abhorrent condition.

 

Also discovered the timing is off by a tooth. Please let me know if I'm missing something, but every other rotation when the crank marks were aligned, the exhaust cam is off.

Can a tooth off cause zero compression or will there still possibly be compression?

 

Didn't have the time to pull the valve cover or figure out when the valves are closed for the leakdown test.

 

Hopefully tomorrow will get that done if the kids cooperate.

 

Speaking of possible replacement options, there is a wrecked 2004 outback xt vin: 4S4BP67C054338355 coming up in salvage auction starting at $800. 347,000 km though! Written off for damage to the side, not front end collision. Thoughts or just too much mileage? No history to say if it ever has had the engine replaced.[ATTACH]279828[/ATTACH][ATTACH]279829[/ATTACH][ATTACH]279830[/ATTACH]

 

The motor isn't easily interchangeable and those motor are unreliable with that many miles. You would have to strip it down to a short block and reused the heads, cams, oil scavenge pump for the low mount turbo from your 2010. The 5th Gyn also has an extra bolt for the oil pan as well.

[dgoodhue]

Okay, so the weekend didn't go as planned, but here we are. Got the timing covers off and found the timing belt in abhorrent condition.

 

Also discovered the timing is off by a tooth. Please let me know if I'm missing something, but every other rotation when the crank marks were aligned, the exhaust cam is off.

Can a tooth off cause zero compression or will there still possibly be compression?

 

Didn't have the time to pull the valve cover or figure out when the valves are closed for the leakdown test.

 

Hopefully tomorrow will get that done if the kids cooperate.

 

Speaking of possible replacement options, there is a wrecked 2004 outback xt vin: 4S4BP67C054338355 coming up in salvage auction starting at $800. 347,000 km though! Written off for damage to the side, not front end collision. Thoughts or just too much mileage? No history to say if it ever has had the engine replaced.[ATTACH]279828[/ATTACH][ATTACH]279829[/ATTACH][ATTACH]279830[/ATTACH]

 

I can't see your attached pictures, but as I mentioned above I had accidentally set my exhaust cam off by gear and I got check engine code similar to what you were seeing, it idled slightl rough but it was driveable. It wouldn't have zero compression.

[FLlegacy]

I can't see your attached pictures, but as I mentioned above I had accidentally set my exhaust cam off by gear and I got check engine code similar to what you were seeing, it idled slightl rough but it was driveable. It wouldn't have zero compression.

 

On the plus side of that, it does sound more like it is a valve not the short block, either way the engine is coming out at this point.

[SaskyGT]

The motor isn't easily interchangeable and those motor are unreliable with that many miles. You would have to strip it down to a short block and reused the heads, cams, oil scavenge pump for the low mount turbo from your 2010. The 5th Gyn also has an extra bolt for the oil pan as well.

Thank you for the input! Are there matching numbers on the engine to be able to tell if it is the original engine or not?

 

I had some issues trying to make a post from my phone last night. Chrome wouldn't let me attach pictures and tapatalk didn't either apparently.

 

Timing belt condition - ignore the timing marks, the crank wasn't lined up

 

These two pictures are a pair - crank is centered and the resulting cams. If I centered the cams, the crank would be almost two teeth over from center (didn't take a picture and can't remember clearly right now)

 

On my 1g DSM, when the one exhaust valve was burnt, there was a hole about the size of a pencil through it. Wouldn't make any compression at low RPM or a compression test but would fire sometimes at high RPM. On this car, it was driveable, but at idle it would sway the whole vehicle side to side in a gentle motion.

 

I'll hold off speculating though until the leak down test is done. But yes, the engine is coming out.

Edited October 7, 2019 by SaskyGT

[FLlegacy]

Thank you for the input! Are there matching numbers on the engine to be able to tell if it is the original engine or not?

 

I had some issues trying to make a post from my phone last night. Chrome wouldn't let me attach pictures and tapatalk didn't either apparently.

 

 

 

On my 1g DSM, when the one exhaust valve was burnt, there was a hole about the size of a pencil through it. Wouldn't make any compression at low RPM or a compression test but would fire sometimes at high RPM. On this car, it was driveable, but at idle it would sway the whole vehicle side to side in a gentle motion.

 

I'll hold off speculating though until the leak down test is done. But yes, the engine is coming out.

 

All cars have a vin tag of some sort on the engine, I cant recall if it is stamped into the block but it is likely somewhere on the short block. You may not find it until the intake manifold and accessories are removed. You can also just check the hardware to see if it is scarred from being removed previously.

[SaskyGT]

Read this entire thread. The early posts are doubtful but the more you read the more they start to understand why the mod was made.

https://forums.nasioc.com/forums/showthread.php?t=2882734

The EJ has fundamental flaw with how the coolant flows through the left hand head and some say the knock sensor location exacerbates this. If you find pictures of blown EJs you'll notice a trend that cylinder 4 is the one the is messed up or looks the worst.

 

Very interesting read once you sort through all the shenanigans that is NASIOC. On the page for Dom's kit, it mentions that it doesn't fit LGT 10+. Is there a particular reason?

[FLlegacy]

You should keep in mind there have been incremental changes to EJ25 engines over the years so what applies to certain model years may not apply to later ones. My understanding of our engines tuning is the ecm listens for knock on cylinder 4 and adjusts timing and fuel accordingly, because that cylinder gets the most heat and the least fuel. OEM designs are limited by all kinds of compromises, this should be no surprise.