Misfire Issues

Well, still having misfire issues with cylinder 4. I'm not getting any stalling or loss of power. The misfires happen on cold startups while idling. I live in Florida, so it's not super cold, but they only occur in the morning within the first 3 minutes of driving. Once the car is warm, it runs with no misfire events. I can idle it all day and get only one or two events. I've changed the plugs and swapped the cylinder 4 coilpack to cylinder 2. Misfire did not move, so I can rule out the coils and plugs. I have not gotten a compression test done yet.

 

Anything you guys can think of that I missed? I have logs and can post them if needed.

 

 

If anyone in the North Florida area has a compression tester I can provide some food and beverages along with any assistance you may need with cars or technology.

Have you swapped injectors yet?

Also, when you say you have a misfire, you do mean the CEL turned on right? Or you are referring to a fairly high roughness count on #4.

 

In any case, if the injector swap and the rest do not fix it, time for leakdown and compression test. From my experience, valve would not be an issue if the misfire only occurs when the engine is cold. The latter issue is usually associated with piston issues (e.g. broken ringland).

Cel is on with a high count on 4. ONLY WHEN COLD though. I can drive all day (and I have) and never have a high count until the car sits.

Yeah. same happened to me on one of my cars (cylinder 2 though). Looks like I have a broken ringland as I inspected the cylinder walls using a borescope. Saw some scratches.

 

Usually, the CEL goes away when the car warms up because metal expands and the cracks are now much smaller, thereby decreasing the probability of misfires. But overtime, it may get worse. I know that's not what you want to hear though.

 

In any case, swap injectors to rule that out first.

yeah done with the car I think.

So the idle rpm on my logs starts at bout 1250 rpm and the misfires don't start to get out of hand until 1093 rpm.

How many miles?

 

So did you swap injectors too or not?

 

kinna same for me: at first start, it's ok, then as rpm slowly decreases, roughness count shows up .

almost 90k

This sucks!

 

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Subbed. I began noticing something similar as well. During cold starts the car seems to be idling differently. It's not smooth, not pops or anything, just not smooth until it warms up. I haven't gotten any cels though. Once a misfire on cylinder 2 about 3 months ago during some spirited driving, but haven't again.

 

Hoping it's nothing serious.

I can make the cel not turn on by keeping the RPM above the point when the misfires happen until the car is sufficiently warm. The cel does not come on instantly, but after reset, can take a few days to come back.

I can make the cel not turn on by keeping the RPM above the point when the misfires happen until the car is sufficiently warm. The cel does not come on instantly, but after reset, can take a few days to come back.

 

I was doing that too to avoid getting a CEL cause I wanted to be able to use my CC.

Might be worth swapping injectors to see if the misfire follows.

Any word on this?

 

I've got a Cylinder 2 misfire, I've already swapped coil packs and new plugs so I guess Injectors is the next step... Although that seems odd because it's only a cold idle issue that clears up when warm. It's quite annoying if I don't let it warm up enough the car will actually stall out when it falls back to idle at a stop.

Any word on this?

 

I've got a Cylinder 2 misfire, I've already swapped coil packs and new plugs so I guess Injectors is the next step... Although that seems odd because it's only a cold idle issue that clears up when warm. It's quite annoying if I don't let it warm up enough the car will actually stall out when it falls back to idle at a stop.

Have you done a compression and leak down test.

 

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Any word on this?

 

I've got a Cylinder 2 misfire, I've already swapped coil packs and new plugs so I guess Injectors is the next step... Although that seems odd because it's only a cold idle issue that clears up when warm. It's quite annoying if I don't let it warm up enough the car will actually stall out when it falls back to idle at a stop.

 

if it only happens at cold idle, then I'd doubt it is the injector. Three more possible causes: vacuum leak due to still using the old design intake orings, cracked ringlands, or possibly valve clearance issue. The latter usually shows up when warmed up though.

 

so if you're still using the old intake orings, change them and see what happens.

if no change, do a compression/leakdown test.

you should also check your valve clearance.

if it only happens at cold idle, then I'd doubt it is the injector. Three more possible causes: vacuum leak due to still using the old design intake orings, cracked ringlands, or possibly valve clearance issue. The latter usually shows up when warmed up though.

 

so if you're still using the old intake orings, change them and see what happens.

if no change, do a compression/leakdown test.

you should also check your valve clearance.

 

http://legacygt.com/forums/showthread.php/diy-rough-idle-cold-start-cold-temps-lgt-07-09-155325p13.html

 

That thread sounds awfully like my issue although I'm unsure if the orings are the same in the newer LGT, I think I read somewhere they were different... Also, I have no way to tell anything about the engine in my car, all I know is that it was replaced at some point and I have this issue and a cylinder 2 misfire code that has been haunting me lately.

 

Maybe I should check for vacuum leaks and go from there... I really don't know...

yeah. I am actually not sure if 2010+ ever suffered from this issue. If you have no way to log, you should definitely consider getting the btssm app with appropriate hardware. It will help you monitor and possibly diagnose your current issue.

 

How many miles do you have? Any mods done to the car?

Mine was a burnt valve on #4. Nothing showed on a leak down or compression check. Also had zero exhaust valve clearance on that cylinder. Exact same issues.

That's the thing I have no clue how many miles are on the engine, it's not original and was replaced by the dealership. I might go ahead and replace the o-rings anyways to find out. Now it seems I'm starting to get misfires all around as well, at least slightly... From my drive home today: 40 on Cylinder 1, 295 on Cylinder 2, 2 on Cylinder 3 and 3 on Cylinder 4. Stalled about 3 times, once it warmed up it ran absolutely flawlessly...

 

Can you do any sort of diagnostics with an Accessport V3? I plan on getting one in the next few days. Is it possible to check the date of my engine? I couldn't really find many markings on it to help me out. Is it possible I have an older EJ255 in my car?

 

Sorry for all the questions I'm a newbie around here and working with these cars.

While the blocks are most likely identical to older models, the heads and intake I believe are going to be specific to the 5th gen. Are you certain the dealer changed the whole engine, or did they give you a reman block? This seems like the more likely scenario given how specific the cams and sensors are to this gen. The accessport only reads codes and logs data, so in that sense it can help you diagnose the issue.

Yeah I thought the data logging could help. The dealer told me the engine was replaced at 120k miles (about 25k miles ago). That's all they really said so I really have no way of knowing where it came from... The part number for the newer/redesigned o-rings appears to be the same but I guess I'll find out pretty soon.

If it was a Subaru dealer, I would think it was a reman possibly a long block, I wouldn't be too concerned about it at this point, I do believe though an engine has a 3yr 36k mile warranty through subaru. You should hold off on the AP and do some logging with btssm or something of that sort that doesn't require an ecu modification just in case.

 

I am pretty sure with the differences in our engines and a standard ej25 turbo it was probably a specific rebuild for our cars, not just a e255 they pulled from a wrecker.

 

Differences from other ej25 turbo motors:

cam driven oil pump

oil pan

dual avcs

water pump

engine mounts-although the actual mounting holes may still be there I haven't checked.

 

These are not small differences if the entire engine was replaced, I think it more likely either it was only a long block, or short block with the accessories swapped from the original motor.

Upon visual inspection the block does look a bit newer. It really ONLY happens in the morning after sitting overnight and if I don't let it warm up for a good 5-10 minutes It'll stall constantly.

 

It looks like it has been to the dealership for this issue because when I've already discovered a brand new injector on cylinder 2 (Which I swapped with another to double check) as well as an autolite plug in JUST cylinder 2. I ended up replacing all 4 with factory NGK's just to be safe... No idea about a warrenty on the engine, the dealership it was originally serviced at is too far from where I live. The closest subaru dealership to me is about an hour away as well.

 

I don't know if its particularly bad because I'm running 93 octane on the stock tune? It shouldn't matter. I could swap injectors but I feel I'd have a misfire all the time if that were the case which I don't.

 

The car runs Fantastic when it's warmed up and logging with btssm seems like a waste if I hopefully do fix the issue and finally get an accessport to likely go stage 1.

While the blocks are most likely identical to older models, the heads and intake I believe are going to be specific to the 5th gen.

 

 

The oil pan has one more bolt hole to fix it to the block on the '10-up LGT motor. It would be possible to drill and tap that extra hole in an earlier block (or one from a WRX or FXT) but I really doubt a dealer would do that.