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Discussion Starter #1
Hey guys,

So my 2014 Focus ST started having a misfire in cylinder 4 this morning. On my way to work I noticed a slight unusual gurgle at low RPM, didn't think much of it other than I need to keep an eye on that and see if that continues. I got back in the car later and on my way home it quickly got significantly worse (it's only a 5 min drive btw), and turned into major hesitation, loss of power, violent shaking, and the CEL turned on and was flashing for misfire. I checked codes on my AP and it gave me P0304 cylinder 4 misfire, P26DE (no description), and eventually misfire on startup. Btw, all I have installed is a Cobb filter and AP3 stage 2 93. I was on stage 1 before but outside temps dropped significantly so I switched to stage 2. Has almost 91k miles.

I've already tried replacing spark plugs (looks like they were never replaced anyway) and it sounded a little better initially but still had a slight gurgle and hesitation at low RPM. CEL came on after about 30 sec. I also decided to check my oil and I had a decent bit of white smoke coming from the dip stick and oil cap, oil level looked okay though (only changed about 800 miles ago). Cylinder 1-3 spark plugs looked old and worn but nothing horrible, but cylinder 4 plug was definitely fouled and covered in black soot and possibly some oil. I saw some people saying the P26DE code could be from the MAF sensor, I know there are mixed opinions about this but could the oiled Cobb filter have gotten on the sensor and is giving bad readings?

When I got the car used I got an extended powertrain warranty with it and I've only put about 5k miles on it since then so I'll try taking it there and seeing what they say, but I wanted to see about getting some other opinions first. I'm gonna try pulling out cyl 4 spark plug again tonight or tomorrow and checking for oil there and examining the cylinder, I'm really hoping I don't have bad rings, but the smoke coming from the oil cap/dip stick is making me think it could be. I didn't have any smoke coming out when I first got the car.
 

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Hey guys,

So my 2014 Focus ST started having a misfire in cylinder 4 this morning. On my way to work I noticed a slight unusual gurgle at low RPM, didn't think much of it other than I need to keep an eye on that and see if that continues. I got back in the car later and on my way home it quickly got significantly worse (it's only a 5 min drive btw), and turned into major hesitation, loss of power, violent shaking, and the CEL turned on and was flashing for misfire. I checked codes on my AP and it gave me P0304 cylinder 4 misfire, P26DE (no description), and eventually misfire on startup. Btw, all I have installed is a Cobb filter and AP3 stage 2 93. I was on stage 1 before but outside temps dropped significantly so I switched to stage 2. Has almost 91k miles.

I've already tried replacing spark plugs (looks like they were never replaced anyway) and it sounded a little better initially but still had a slight gurgle and hesitation at low RPM. CEL came on after about 30 sec. I also decided to check my oil and I had a decent bit of white smoke coming from the dip stick and oil cap, oil level looked okay though (only changed about 800 miles ago). Cylinder 1-3 spark plugs looked old and worn but nothing horrible, but cylinder 4 plug was definitely fouled and covered in black soot and possibly some oil. I saw some people saying the P26DE code could be from the MAF sensor, I know there are mixed opinions about this but could the oiled Cobb filter have gotten on the sensor and is giving bad readings?

When I got the car used I got an extended powertrain warranty with it and I've only put about 5k miles on it since then so I'll try taking it there and seeing what they say, but I wanted to see about getting some other opinions first. I'm gonna try pulling out cyl 4 spark plug again tonight or tomorrow and checking for oil there and examining the cylinder, I'm really hoping I don't have bad rings, but the smoke coming from the oil cap/dip stick is making me think it could be. I didn't have any smoke coming out when I first got the car.

Compression test, don't run the stage 2 map without a fmic, and you probably have a blown ringland. Comp test will confirm.
 

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Will do, and yeah I'll be going back to stage 1 until I get an FMIC to be safe.
Also, swap the #4 coil pack to a different plug, see if the misfire follows. Could be a bad coil pack, but its not very common. Blown ringlands is very common.
 

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Discussion Starter #5
Also, swap the #4 coil pack to a different plug, see if the misfire follows. Could be a bad coil pack, but its not very common. Blown ringlands is very common.
Yeah I'll definitely try that tonight too. I work at a Ford dealer but I got the car used at Honda when I used to work there, so that's where my warranty's at. I'll try swapping coil packs tonight but if that doesn't give me any sort of answer I'll see if a diag guy can take a look at it tomorrow at Ford, otherwise I'll probably just drop it off at Honda. I'm hoping it's not rings, but that's what a warranty is for, right? 🥵
 

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If you can get them to cover it, do you have any mods?
 

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Discussion Starter #7
If you can get them to cover it, do you have any mods?
Cobb AP3 and Cobb filter. Ford can't take it until tomorrow so I'll uninstall the AP tonight. Also I tried swapping coil packs today and while I was in there checked the plug and cylinder too. The brand new spark plug was already black and a little wet, and I put an endoscope in the cylinder and had a puddle of oil and some fuel sitting in there. So looks like my ringlands are done. Guess we'll get the final verdict tomorrow.
 

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Just so you know even when it's cold af out the stock intercooler sucks. I watched my charge Temps hit about 140 on a pull and it was under 39*out.

Sent from my BND-L34 using Tapatalk
 

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Discussion Starter #9
Just so you know even when it's cold af out the stock intercooler sucks. I watched my charge Temps hit about 140 on a pull and it was under 39*out.
Yeah when it's warmer out I'm easier on it, when it's cold enough though and I do a pull I haven't seen it go past around 100.
 

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Took it Honda this morning (since that’s where my warranty is from, and to get a loaner), they did a quick inspections and determined it’s piston rings. So they took it over to Ford and they’re gonna be doing full diag and repair soon, most likely looking at a new motor, or at least a short block. Unfortunately they’re saying it could be a few weeks at least, but it sounded like they’re gonna try to prioritize my repair since I’m an employee. Wish me luck :/
 

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Discussion Starter #11
So the inspector from the warranty company came to check out my car on Wednesday, apparently he didn't take enough notes on it or something lol, so they want us to do a drop test to confirm it's not a dropped valve that's causing low compression and the oil to leak into the cylinder, so hopefully that test will be done today, and then they should approve the repair next week. Btw, looks like I'll be getting a brand new long block, so that's a plus.
 

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Discussion Starter #12
Drop test went well, definitely blown rings. New long block got approved by the warranty company so that’ll be getting shipped this week and hopefully will be done next week!
 
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