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Discussion Starter · #1 ·
I'm running a stage 2 setup on my car for the last couple of months. My car is a 2018 STi and just over 25000 miles on it with a catted downpipe, exhaust, cobb sf intake, aem fuel pump, cobb fuel regulator, boost controller, ngk spark plugs and pitch stop mount. The car was stage 1 for most of it's life and never gave me an ounce of trouble. Since going stage 2 at about 23500 miles, I'm now experiencing check engine lights every 50-100 miles and my accessport is telling me it's a cylinder 4 misfire. The car begins to vibrate on startup and idle and then the dash lights up after Ive reset the ecu learning and driven for about 50 miles or so. I don't drive the car hard, launch it or anything like that. It's well maintained as is basically a commuter car. The car is currently sitting at a Subaru dealer service department. My tuner who is reputable said there isn't much he can do, but it could be a mapping issue that he needs to retweak something. But the vibration on startup is very unsettling, and my gut is telling me potential ringland failure is waiting around the corner. Another friend suggested doing a compression test. I'm not sure where to go from here. But something tells me I'll be having to order a new shortblock in the near future. I guess my question is what would you guys do in my situation? Any input on how to proceed would be appreciated.
 

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The dealer should be able to diagnose a fuel or spark issue. A compression test is the obvious next step, but if it had a cracked ringland you should notice a miss when its cranking to start. My car recently popped a cylinder from a full boost partial throttle issue from a bad tune. Cylinder 2 60psi 80% leakdown. It ran and idled perfectly with no missfires or CEL. It just cranked funny and it was more noticeable when holding the gas pedal down to let it keep cranking. I bet ringland isnt your issue.
 

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Discussion Starter · #3 ·
The dealer should be able to diagnose a fuel or spark issue. A compression test is the obvious next step, but if it had a cracked ringland you should notice a miss when its cranking to start. My car recently popped a cylinder from a full boost partial throttle issue from a bad tune. Cylinder 2 60psi 80% leakdown. It ran and idled perfectly with no missfires or CEL. It just cranked funny and it was more noticeable when holding the gas pedal down to let it keep cranking. I bet ringland isnt your issue.
It doesn't have a problem starting. I mean, maybe it's a faulty coil at this point. As I said I replaced all the spark plugs when I went stage 2. Maybe I should think about fuel injectors at this point.
 

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Discussion Starter · #5 ·
Is this obvious when this happens or is it more like a longer crank time before starting?
The car starts up just fine. When the revs start to come down the engine starts to vibrate a little more than usual. My tuner said he can’t erase potential faulty codes with what I’ll refer to as the new “Cobb accessport laws”. Which is also frustrating. He’s also busy and I’m thinking he almost doesn’t want to be bothered to help me resolve it. And the dealership said they can’t do anything either because the car, “has a tune on it”. It’s like I’m stuck between a rock and a hard place. What am I supposed to do, just live with a broken car? 😔
 

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Sorry the hear that, are there any more tuner's in your area's that could help? I know the shops in my area (Northern VA, DC, MD) also do repairs. Maybe even having your car shipped out to a good shop could be an option? If that's not an option, how easy would it be to return it to stock?
 

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Discussion Starter · #7 ·
Sorry the hear that, are there any more tuner's in your area's that could help? I know the shops in my area (Northern VA, DC, MD) also do repairs. Maybe even having your car shipped out to a good shop could be an option? If that's not an option, how easy would it be to return it to stock?
Yeah I mean I’m in Ny there are other shops I could bring it to for a retune I suppose. Would putting in a stronger block and forged pistons maybe fix it?
 

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Is this obvious when this happens or is it more like a longer crank time before starting?
It sounds different. In my experience, it will sound like when you pull spark plugs to do a compression test for that compression stroke. Best way to hear it is to pull a single spark plug and turn the car over with fuel pump fuse removed and/or pedal floored. You'll hear a distinct difference in turning effort/speed from the starter on that compression stroke.

An example (not an EJ, but same idea):

If you pull a plug and try this and there is no difference... 😬

...

OP if I was in your position, I would test/confirm my fears/assumptions. Start with the easiest stuff to reassure yourself that it isn't broken. Remove the fuel pump fuse with the car running so it runs out of fuel. Then, press the throttle to the floor and turn the car over to hear how it cranks. Does it sound like any cylinder is off? If you aren't sure what I mean, try and imagine one cylinder has the spark plug removed as in the video I posted above.

Next, try removing the oil cap with the car at idle and slowly revving the car to 2k. I'd put a rag around the area of the oil fill for small spatters/droplets that come out, though when I did this test even that wasn't necessary... Do you get that rush of air being pulled in once RPMs rise? Or do you get a LOT more air coming out of the oil cap (blowby). If that isn't reassuring, I'd probably move on to a compression/leakdown test just to settle it in my mind.

While doing a compression test, if you find one that is low on compression, I'd lock the engine at TDC on that cylinder and pressurize it with the same hose w/schraeder valve removed and try and identify where the air is going. Likely, it's ring land if you have low compression, but again it's nice to test your assumptions so you know what you are looking at.

I also don't know that I'd put much effort/resources into the dealership. If it's a broken ring land, they (SoA and your dealership) probably aren't going to help given it's tuned. And if it isn't a ringland, they've already said there isn't anything they can do since it's tuned. So... IMO not much value in having them do anything.
 

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Are you pro tuned?
I may be asking a dumb question but a lot of your mods are things you should tune for
 

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so have you tried swapping the plug/coil pack and seeing if it follows to the new cyl?

this could be a tuning thing, or it could be mechanical. it's really hard to tell over the internet.
following what nissan said, figure out what exactly is the issue and go from there, if it is a new shortblock that is needed, while that sucks, there are plenty of options for that.
 

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Discussion Starter · #12 ·
so have you tried swapping the plug/coil pack and seeing if it follows to the new cyl?

this could be a tuning thing, or it could be mechanical. it's really hard to tell over the internet.
following what nissan said, figure out what exactly is the issue and go from there, if it is a new shortblock that is needed, while that sucks, there are plenty of options for that.
I haven't had a chance to get around to it. The dealership just reset my CEL code and sent me on my way. I have to find a private mechanic or friend in my area that knows what they're doing to do that.
 

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Discussion Starter · #15 ·
If you still have the parts, you could try reverting to stage one (or stage 0/stock) and see if that fixes it.
So the plot thickens. Any maybe some of you are more familiar with Cobb's new Green update and can shed some light on this. Basically it's boiling to my tuner said he needs to tweak the tune for cylinder 4 mapping. And from the research I've done, some tuners have a grace period to use the old Cobb software for tuning. My car was tuned prior to the update, sometime in early March. My tuner also said he needs to use to old software to retune me, and he isn't ready to open up his window to use said software. Which kind of leaves me in limbo, but it is what it is. He said he'll still perform the coil/plug switcharoo and compression test, but said it isn't necessary. The only part I don't understand is why can't I be retuned under the new software? Given the fact I'm fully emission compliant as far as I know.
 

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Well if this new development rules out a cracked ringland, hey that's a win right? XD

I don't know enough about the Cobb "ecosystem" to know. I'm sure others who are more knowledgeable will chime in though.
 

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So the plot thickens. Any maybe some of you are more familiar with Cobb's new Green update and can shed some light on this. Basically it's boiling to my tuner said he needs to tweak the tune for cylinder 4 mapping. And from the research I've done, some tuners have a grace period to use the old Cobb software for tuning. My car was tuned prior to the update, sometime in early March. My tuner also said he needs to use to old software to retune me, and he isn't ready to open up his window to use said software. Which kind of leaves me in limbo, but it is what it is. He said he'll still perform the coil/plug switcharoo and compression test, but said it isn't necessary. The only part I don't understand is why can't I be retuned under the new software? Given the fact I'm fully emission compliant as far as I know.
you arent running flex fuel right? if you are not, based on my understanding, you should be able to be tuned with the new software. although some cats will throw a code, not sure if yours will or not, i'm not as well versed in which ones work and which ones dont.
 

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Discussion Starter · #19 ·
Well if this new development rules out a cracked ringland, hey that's a win right? XD

I don't know enough about the Cobb "ecosystem" to know. I'm sure others who are more knowledgeable will chime in though.
Most definitely will be a win! I wasn't really looking forward to shelling out 10k for a new shortblock.
you arent running flex fuel right? if you are not, based on my understanding, you should be able to be tuned with the new software. although some cats will throw a code, not sure if yours will or not, i'm not as well versed in which ones work and which ones dont.
No just a 93 tune. And a Grimmspeed catted downpipe. But we did put a spacer on the o2 because hit air kept frying the sensor on the downpipe. I just remembered that. I don’t want to assume but I don’t think he would’ve deleted the O2 sensor code for the downpipe, or could he have.
 
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