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Discussion Starter #1
Hello everyone so on my drive home today, my 2014 2.0T had three lights come on at once while passing someone on the freeway, check engine light flashing along with traction control and stability control, I also think i heard a noise from the engine but since I had the radio up I cant say what exactly it was, I immediately thought my car had suffered the piston failure issue and started making for a freeway off ramp, check engine light stopped blinking and turned off entirely, traction control and stability control lights were still on, no smoke noise or any other noticeable issues. I was very close to home and managed to limp it the rest of the way home without incident. I scanned for codes when I got home, it had one pending code P0300. I am beyond freaked out, does this sound like the piston issue or could it be something else causing the misfire? I have a day already scheduled to get it to the dealer and I am trying to decide if I should slowly limp it the 5 or so miles there or just have it towed as well as possible peace of mind.
 

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There are a lot of things that can cause a misfire other than piston failure and most of those are far more probable. The traction and stability systems shut down when there is any significant performance issue with the engine so those aren't anything to worry about at this point.

Poor quality gas is listed as a potential misfire cause for good reason because it does happen. I had that happen with my 2008 CTS while on a trip and got the misfire while pulling a mountain grade and it occurred shortly after a fuel fill. After running that tank down to the 1/8 level, avoiding heavy engine load during that time, I filled back up and the problem was gone. Have you filled up recently?

P0300 is set when there is a frequent but inconsistent misfire involving one or more cylinders. A weak coil can cause this to occur because it is no longer able to properly ignite the mixture with the engine running at high RPM and load, the same is true of a failing spark plug. Other potential causes include a problem with the MAF or MAP sensors.

I would start with: don't panic because there is a good chance it isn't a major engine problem. If the fuel is at half a tank or lower fill up with premium at a top tier supplier. Run some of that through and then try the engine again at increased load/rpm and see if the misfire continues. If you get a misfire, reduce the load on the engine so that it goes away because you don't want sustained raw fuel going into the cats. Misfires do happen and although the ECM keeps a running count, it won't set a DTC until a threshold is met because otherwise drivers would be experiencing frequent nuisance CEL illumination. If the misfire continues, a service shop will be able to do real time logging of misfire counts by cylinder which will let them narrow the problem down pretty quickly.

Rodger
 
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Its going to be all in the idle, for me i had those lights come on and check engine, it wasnt flashing at the time. Having it just run i heard how it sounded different, and thats when i knew piston failed on me. Of course i suspected it because my car only had 27000 km on it, then made it clear once i did a compression test cylinder 3 cracked. Now if you have warranty just drive it there if any more damage is caused you got it covered, now out of warranty might wanna tow it less load is better if trying to save the engine. Seeing yours might be out of powertrain warranty might be an issue, keeps us updated i hope its not mechanical.
 

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Discussion Starter #4
There are a lot of things that can cause a misfire other than piston failure and most of those are far more probable. The traction and stability systems shut down when there is any significant performance issue with the engine so those aren't anything to worry about at this point.

Poor quality gas is listed as a potential misfire cause for good reason because it does happen. I had that happen with my 2008 CTS while on a trip and got the misfire while pulling a mountain grade and it occurred shortly after a fuel fill. After running that tank down to the 1/8 level, avoiding heavy engine load during that time, I filled back up and the problem was gone. Have you filled up recently?

P0300 is set when there is a frequent but inconsistent misfire involving one or more cylinders. A weak coil can cause this to occur because it is no longer able to properly ignite the mixture with the engine running at high RPM and load, the same is true of a failing spark plug. Other potential causes include a problem with the MAF or MAP sensors.

I would start with: don't panic because there is a good chance it isn't a major engine problem. If the fuel is at half a tank or lower fill up with premium at a top tier supplier. Run some of that through and then try the engine again at increased load/rpm and see if the misfire continues. If you get a misfire, reduce the load on the engine so that it goes away because you don't want sustained raw fuel going into the cats. Misfires do happen and although the ECM keeps a running count, it won't set a DTC until a threshold is met because otherwise drivers would be experiencing frequent nuisance CEL illumination. If the misfire continues, a service shop will be able to do real time logging of misfire counts by cylinder which will let them narrow the problem down pretty quickly.

Rodger
I had actually had my tank down pretty low the other day before my last refill, maybe 40miles left on range, i only fill up with premium at costco. It's a huge relief to hear that there are a lot more likely causes, my service advisor said based on what I told him he thinks its safe to drive as long as I take it slow and if it feels safe to me, so tomorrow I am going to leave work two hours early so I can get in and slowly make my way their, should give me plenty of time also in the event I feel I need a tow truck.
 

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It doesn't matter WHERE you buy your gas, you could have gotten some bad fuel. As long as the CEL isn't flashing and the car is running fairly normally then you don't need a tow truck. Cars have been screwed up being loaded on a flatbed and a tow truck has even more bad possibilities so don't have it towed prematurely.

Keep your receipt from Costco in case the dealer determines you got a load of water or other contaminants in the fuel. All it takes is one poorly maintained tanker truck to have fuel contamination.

Rodger
 

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It doesn't matter WHERE you buy your gas, you could have gotten some bad fuel. As long as the CEL isn't flashing and the car is running fairly normally then you don't need a tow truck. Cars have been screwed up being loaded on a flatbed and a tow truck has even more bad possibilities so don't have it towed prematurely.

Keep your receipt from Costco in case the dealer determines you got a load of water or other contaminants in the fuel. All it takes is one poorly maintained tanker truck to have fuel contamination.

Rodger
There's this one brand of gasoline around here, where it seems that at least once every couple of years, water gets into their truck. It makes the news, showing that cars after a fill-up would travel about 1/2 a mile or so down the road and then totally stall out. Considered rare, but it does happen.

With code P0300, I would have someone check the coils. If you've driven with it for too long afterwards, you will also be looking at having to replace the Cat Converter as well, very soon.
 

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Discussion Starter #7
There's this one brand of gasoline around here, where it seems that at least once every couple of years, water gets into their truck. It makes the news, showing that cars after a fill-up would travel about 1/2 a mile or so down the road and then totally stall out. Considered rare, but it does happen.

With code P0300, I would have someone check the coils. If you've driven with it for too long afterwards, you will also be looking at having to replace the Cat Converter as well, very soon.
I didn't drive for very long the day this happened. And the remainder of my dr ive home I babied it. Hopefully if the car is otherwise fine and it ends up being something like the cpils, the cats aren't toast..
 

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As long as is NOT actively misfiring, the cats will survive. The reason for the flashing (instead of steady) CEL is to warn you of a misfire condition and the need to immediately change your driving behavior to avoid damage to the cats and it sounds like you did so they will be fine. Raw fuel going into the cats will quickly overheat them leading to damage and potentially vehicle fire in extreme conditions but you didn't approach those conditions during your short flashing CEL experience.

The cats are purposefully fed some unburned hydrocarbons during initial cold start to heat them rapidly in order to meet cold start emissions standards in the allotted time. During that typical 10-30 second period, the ECM sets the mixture to a highly enriched state and the timing is severely retarded so complete combustion doesn't occur within the cylinder/cylinder head and your brief CEL won't have done any more than what happens during a typical winter start. Although the exhaust smell is typically "cleaner" from a cat equipped vehicle, during a cold start OR when the engine is under extreme load you will often get odor from the cats.

Given that you had filled up shortly prior to this happening, I wouldn't be at all surprised if the fuel is the issue. If this resulted from bad fuel, you can claim any damage/repair expense from the comprehensive section of your insurance and their subrogation department will go for reimbursement from the fuel provider.

The dealer should run a live view log of the car under load and it will show whether it is randomly misfiring across multiple cylinders (generally a fuel or fuel mixture issue) or if it is confined to one or two which then makes a coil, plug, or injector the more likely culprit. Misfiring triggering a CEL is an area where the ECM diagnostics will generally lead pretty quickly to the underlying cause.

Rodger
 

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Discussion Starter #9 (Edited)
Just dropped my car off at the dealer. Drove it there without incident, something doesn't feel right for sure, very slowly got it up to freeway speeds and at one point it sort of stuttered or stumbled but otherwise felt fine, no lights on on the drive over. I am very relieved as I would think if this was some sort of severe problem it would have been more apparent. Will post again when I find out more.
 

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Just dropped my car off at the dealer. Drove it there without incident, something doesn't feel right for sure, very slowly got it up to freeway speeds and at one point it sort of stuttered or stumbled but otherwise felt fine, no lights on on the drive over. I am very relieved as I would think if this was some sort of severe problem it would have been more apparent. Will post again when I find out more.
Sometimes, these things get strange. I have had misfires with NO SES lights. But when I called OnStar on the fly, they did say something was wrong and that I needed to get the car serviced asap. That was on the 3.6 CTS. I was told by an independent mechanic that the stutter I was getting was indeed a misfire and to get the coils checked.
 

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The ECM is constantly counting misfires but it doesn't turn on the flashing CEL until the safe threshold is passed in order to avoid nuisance CEL activation. Sporadic misfires/partial fires are common and there is no need to worry the owner for those events, only when it becomes frequent enough to indicate there is a problem.

The precision sensor for crankshaft speed is capable of measuring very rapid variance in rate of change and it expects that there will be a pulse every time a combustion event occurs and if that change doesn't occur or is less than expected then a misfire is logged for that cylinder and if the count exceeds the allowable threshold then the CEL is turned on in flashing mode to indicate a current significant misfire. Even when it doesn't reach this state, the ECM is recording these counts by cylinder and that data is available via code reader (and OnStar). The crankshaft speed sensor array is extremely sensitive and accurate, GM uses this same process to dynamically fine tune the injector calibration on their diesel engines so that each cylinder produces the same power contribution with very precise adjustment capability.

Rodger
 

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Discussion Starter #12
Back from the dealer! Car isnt repaired yet but the issue was simple. Needs new coils, 2 of the 4 were failing, simple repair so asked to do the parts so I could do it myself, dealer didn't have the coils on hand and wouldn't be able to get them before I would need my car again so I got the part number from them and ordered them myself, going to replace all 4 to be safe. My car should be back to normal next Tuesday!
 

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Replace all 4 plugs at the same time unless that has been done very recently.

Rodger
 

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Sounds okay then Locomotive. A failing plug stresses the associated coil pack either through letting the peak voltage rise higher than normal due to a wide gap or increasing the peak current during discharge due to a fouled and leaky insulator. That is why typically when a coil pack is replaced the associated plug also gets checked to make sure it wasn't the root cause of the failed coil.

Rodger
 
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