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2017 ST3-Stroked and Cornfed
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Discussion Starter · #1 ·
So I'm really baffled on what is going on with this car.
Its a 2017, 2.3 stroker, G25-660.

The car started running lean under throttle and breaking up after using the Cobb FFS feature, since it cuts fuel. It developed a break-up under any sort of boost.
The car developed the nefarious Random misfire code with the flashing engine light, and has had a specific misfire code for every cylinder except #2.
So I assumed the breakup was a plug issue so I decided it was time to swap plugs. The car is running the Ruthenium plugs at .026. I pulled the pictured spark plug out of cylinder 3 and was kinda shocked.
I decided it was worth compression testing and the results are far from perfect, but still within acceptable measures based on my previous knowledge.
1-178
2-192
3-194
4-194
The first cylinder also had some damage to the porcelain. I bore-scoped these cylinders and then the other two and couldn't see anything other then pretty knarly carbon buildup on the top of #3.
I then changed the plugs to some brand new ruthenium plugs gapped at .026 also.
I suspected bad gas, and then immediately replaced it with known fresh 93 and no change.
The car is not eating coolant or oil, and isn't overheating by pressurizing the coolant system.
The AP is noticing the car is doing max cylinder correction
I checked the plugs after 100 miles of just driving and they appeared to be just fine.
I also swapped two coils to see if the codes would follow. It did not but I intend to do that one more time since #3 was swapped with #1 and #4 is the most consistent.
The car otherwise, free-revs clean with no breakup, the idle is fine and the car cruises fine other then a barely noticeable noise increase, which I presume is the car missing intermittently.

The only other thing I can do realistically is a leakdown, but I'm waiting to be able to use a friends gauge setup.

This is mostly recording what's going on with it and I can post the results when I find out what's wrong with it but if anyone has any input to add I would absolutely appreciate it.
 

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Monitor FRP actual vs desired.

This is sounding like a failed HPFP.

Your compression looks good honestly, 160 is typical.
 

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Monitor FRP actual vs desired.

This is sounding like a failed HPFP.

Your compression looks good honestly, 160 is typical.
He's a built stroker, not sure what comp ratio he is really at.

Over 10 percent deviation, and a HUGE chunk of ceramic decided to break dance in the combustion chamber. That cylinder/ those exhaust valves have got to be hurt.
 

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He's a built stroker, not sure what comp ratio he is really at.

Over 10 percent deviation, and a HUGE chunk of ceramic decided to break dance in the combustion chamber. That cylinder/ those exhaust valves have got to be hurt.
Ahh I didn’t catch that initially
 

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2016 ST2, Absolute Black, Monster FMIC, GFB DVX+ BPV, ALEX' Shift Bushings, PCV-OCC, Innovative RMM
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What mileage?
How long tuned?
How much Hp and fuel you actually need to run?

Do you have an idea what cracked the porcelain?
Overtightened, shipping damage, ...?
Good that new plugs looked OK.

Purge valve can cause lean misfire conditions too.

The stroker gets the higher psi vs stock.
 

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2017 ST3-Stroked and Cornfed
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Discussion Starter · #6 ·
He's a built stroker, not sure what comp ratio he is really at.

Over 10 percent deviation, and a HUGE chunk of ceramic decided to break dance in the combustion chamber. That cylinder/ those exhaust valves have got to be hurt.
Cyl #3 had the ruined plug, and the one with the lowest was #1.
Also, this SHOULD be factory compression.
What mileage?
How long tuned?
How much Hp and fuel you actually need to run?

Do you have an idea what cracked the porcelain?
Overtightened, shipping damage, ...?
Good that new plugs looked OK.

Purge valve can cause lean misfire conditions too.

The stroker gets the higher psi vs stock.
The plugs were absolutely wrenched in there and took unreasonable effort to get them out. 54k miles. Its a built engine/big turbo so the how long tuned seems like a question that doesn't add up to the grand scheme of things. I'm unsure how a plug would be so damaged in such a time from my first drive of the car to now but there is no way its good news.

I just verified with SP63, the comp. ratio of this setup is 9.3:0, so factory.
 
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I had issues with my purge valve and the FRP actual vs desired is what gave me the data to figure it out. I would mostly have issues low throttle easing into a roll from a stop or a high load starting off up a hill with normal throttle. Any time i would floor it things looked ok. Changed the purge valve and it all cleared up for me. I'm on a 2.3L build as well. Did you build yours after the stocker blew up? I feel like my purge valve was the cause of my stocker dying. I just couldnt figure it out until I put my built 2.3L in there and had weird issues like that come up.
 
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Discussion Starter · #8 ·

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Discussion Starter · #9 ·
I had issues with my purge valve and the FRP actual vs desired is what gave me the data to figure it out. I would mostly have issues low throttle easing into a roll from a stop or a high load starting off up a hill with normal throttle. Any time i would floor it things looked ok. Changed the purge valve and it all cleared up for me. I'm on a 2.3L build as well. Did you build yours after the stocker blew up? I feel like my purge valve was the cause of my stocker dying. I just couldnt figure it out until I put my built 2.3L in there and had weird issues like that come up.
I unfortunately got this car setup exactly how it is. So I’m playing the fix it game after it broke with not a lot of prior knowledge lol
 

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From what i can hear from the video, it sounds like you're flooring it below 3000rpm. Is this true?
 

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Discussion Starter · #11 ·
From what i can hear from the video, it sounds like you're flooring it below 3000rpm. Is this true?
That was 4th gear starting around 3200RPM. I also was not pedal to the floor at all, was close on the last one but under WOT right now the car stumbles like I've just hit a rock in the road.
 

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Its hard to tell with a video, if you could datalog while recreating the issue it will help.
 
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That was 4th gear starting around 3200RPM. I also was not pedal to the floor at all, was close on the last one but under WOT right now the car stumbles like I've just hit a rock in the road.
Okay. After rewatching the video, i notice you're pulling HUGE amounts of ignition corrections. That's really bad.
 

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Discussion Starter · #15 ·
Okay. After rewatching the video, i notice you're pulling HUGE amounts of ignition corrections. That's really bad.
Yeah I guess I didn't stress that enough in the original post but it is there. I was worried this would mean timing had jumped but this is a keyed setup. I'm imagining the leakdown test is going to tell me a lot. At this point I'm guessing the piston to cylinder wall seal is compromised, given that the oil cap breather was puking oil all over the valve cover on a short trip.
If the leakdown goes south, I'll have no choice but to split it and see what I find. I think my biggest hang up is that I cant forsee this happening in a weeks time since I've owned it, but at least if the engine needs some service the rest of the car should be fine.
 

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Yeah I guess I didn't stress that enough in the original post but it is there. I was worried this would mean timing had jumped but this is a keyed setup. I'm imagining the leakdown test is going to tell me a lot. At this point I'm guessing the piston to cylinder wall seal is compromised, given that the oil cap breather was puking oil all over the valve cover on a short trip.
If the leakdown goes south, I'll have no choice but to split it and see what I find. I think my biggest hang up is that I cant forsee this happening in a weeks time since I've owned it, but at least if the engine needs some service the rest of the car should be fine.
The timing of this all is unfortunate, but there are several possible causes.

The fact that one of the spark plugs shattered sort of leads me to believe it was a detonation event, whether it was LSPi, or the severe abuse to the internals created when doing your first few no-lift-shifts.
 

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Discussion Starter · #17 ·
Looked like close to -6 degrees.
I will also mention, somehow cylinders 1, 2 and 4 all had +2.50-3.00 degrees before I swapped coils from 1/3, and cylinder 3 was the only cylinder that was negative. After the swap they all seem to go into the negative. I am not privy on how to load up and read AP logs but I can maybe try to post it here so you guys can eyeball it also. Leakdown was a goal after the compression and [email protected] backed that up.
 

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Yeah, you're pulling tons of timing, so something is definitely hurt. Hopefully the leak down test gives you some better answers. Sorry, man.
 
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Discussion Starter · #19 ·
The timing of this all is unfortunate, but there are several possible causes.

The fact that one of the spark plugs shattered sort of leads me to believe it was a detonation event, whether it was LSPi, or the severe abuse to the internals created when doing your first few no-lift-shifts.
This is what I think. On my first little race with a buddies mustang, I used the Cobb FFS and I probably made it through all of 3rd gear before I realized it was at 13.9-14.4 AFR at WOT. Something I seriously didn't expect, and I've been out of it as much as possible. I have been driving it unfortunately to try to diagnose and was suspecting fuel, which turned out to not be the issue.

The guy did warn me not to make a pull under 3K, and with the history having an ecoboost mustang and watching people blow those up in 6th gear, I try to never go more then half throttle in 6th even above 2500 or so.
 

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Discussion Starter · #20 ·
I also wanna add this car miraculously doesn’t smoke out of the exhaust a bit.
 
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