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Discussion Starter #1
My son's 2015 Elantra SE (manual) engine stalled suddenly while driving, only a minute or so after starting in a cold morning. He revved it up to about 3-3.5k in first gear, felt that the car was not responding to the gas pedal, switched to second gear, and the engine stalled. The check light came on. It's a 4-year old car, with about 37k miles on it.

He parked it on the side of the road. He was able to start it again (there is no problem starting it), drive it a bit, but then the stalling happened again.

I checked the codes using an Actron OBDII: P0300, P0302, P0303 (P0304 PD also). So, misfiring of #2 and #3, and possibly #4 cylinders. I cleared the codes, and couldn't reproduce the misfiring.

I checked the coils and the spark plugs. All spark plugs look fine. The coil resistances are all within specs. The coils look clean, except for a bit of scuffing close to the top for #1, #3, and #4. If the scuffing causes arcing, could this cause the misfiring? Notice that the #2 coil doesn't show any damage, but the cylinder is misfiring. Interestingly, the scuffing of all 3 coils is at the same location. The car has not had any accidents.

I'd appreciate any thoughts. I've read related threads, including the horror diagnosis of cracked head gasket, and piston rings, etc, but, I'd appreciate advice that excludes the horror scenario.

Many-many thanks
 

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Discussion Starter #4
Thanks grcauto. I suppose the question is whether the scraped surface of the coils (where the arrows point to in the picture) could cause arcing.
 

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Thanks grcauto. I suppose the question is whether the scraped surface of the coils (where the arrows point to in the picture) could cause arcing.
Look at the same place in the holes and see if there's evidence of arcing through to the head/plug hole. If you see carbon tracks you know it's misfiring.
 

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Discussion Starter #6
Look at the same place in the holes and see if there's evidence of arcing through to the head/plug hole. If you see carbon tracks you know it's misfiring.
No carbon deposits, coil holes look clean. I also checked the crankshaft position sensor: its resistance is within specs too.

Any ideas on what may have caused the random misfiring of 3 out of the 4 cylinders? Contaminated fuel?

Thanks
 

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35k on a four year old car. I would guess maybe a chunk of carbon came off and fouled some plugs for a few. Burned off and now running fine. I’d take it down the freeway for a good hot run.
 

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Discussion Starter #8
35k on a four year old car. I would guess maybe a chunk of carbon came off and fouled some plugs for a few. Burned off and now running fine. I’d take it down the freeway for a good hot run.
I have some additional information:

a. Apparently, this was the 3rd time in the last 18 months that the stalling happened. In all cases, it happened after revving up with a cold engine.

b. I was able to reproduce it: engine is cold; it starts without a problem; I let it idle for a minute or two; then rev it up to 4-4.5K and let it return to idle; idle RPM cannot be maintained and fall to zero; engine shuts down. No engine light; no codes.

c. When the engine has reached normal operating temperature, idle RPM are maintained, engine won't shut down.

What to check?
Thanks
 

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Either software or possibly coolant sensor telling the computer the engine is warmer than it actually is, cutting fuel, and starving it after revving. When it completely warms, the fuel cutoff then becomes normal, engine doesn’t die because it doesn’t need richer mixture, if that makes sense.
 

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After 190,000 on my 13 Elantra I had a similar issue. Cylinder #1 misfiring. Replaced coil and that fixed it. It had similar marks to yours.
 

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Discussion Starter #13
Update

It's probably software to protect a cold engine. Why the high RPM?

I think that the coil damage (the coating has peeled off) is not normal, especially since the damage is in 3 out of the 4 coils (the 4th one also shows the beginning of the coating deterioration), and in all 4 coils the coating deterioration appears at the same location. I think this points to a manufacturing defect. Couldn't this be the source of an electric leakage, that, in turn, causes the misfiring?


To answer your question: the 3rd time the engine stalled, my son was at a stop sign. He then made a left turn, and accelerated in first gear (that's the "high" RPM), before trying to switch to second gear. The engine stalled as the RPM dropped during the switching. I don't find anything unusual about his actions, and I find it very dangerous that the engine stalled, with other cars coming behind him. I find it hard to believe that the software would be limiting this kind of driving to protect the engine (and kill the driver).


As I said, I was able to reproduce the problem with the engine cold, while revving to 3.5-4K, after a few minutes of warming-up the engine. I don't believe the stalling to be normal software-driven operation.


I took it to the dealer: they were, as predicted, unable to reproduce the problem, unable to retrieve the codes, and declined to even pull the coils out, even though I showed them the pictures. Quite aggravating... As if I didn't have anything better to do than spend the day arguing at the dealership.


I think Propflux01 mentioned the possibility of a faulty coolant sensor, which makes sense to me and it is cheap to change. If this doesn't work, I'll probably replace the coils.


Any last thoughts?


Thank you again
 

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Discussion Starter #15
Wouldn't this fall into the warranty period, or did you buy it used?
We bought it new, and, of course, it is under warranty. But, the dealer was not able to reproduce the engine stalling problem, and then refused to do anything else. They refused to pull the coils out: they said that even if they are damaged, Hyundai won't let them replace them because there is no code indicating a problem. They refused to investigate the stalling problem, because the mechanic was able to drive the car, and "everything looks fine". They did a "21-point inspection" and they recommended front brake pads... The service manager did not deny that the picture I showed her indicated coil damage, and even had the audacity to ask me why didn't I complete the repair by replacing the coils (i.e., why didn't I pay out of my pocket $200-$300 to replace warranted parts in a 39K car)...

The problem exists, and I need to get to the bottom of it. That's why I turned to the forum.

Thanks
 

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We bought it new, and, of course, it is under warranty. But, the dealer was not able to reproduce the engine stalling problem, and then refused to do anything else. They refused to pull the coils out: they said that even if they are damaged, Hyundai won't let them replace them because there is no code indicating a problem. They refused to investigate the stalling problem, because the mechanic was able to drive the car, and "everything looks fine". They did a "21-point inspection" and they recommended front brake pads... The service manager did not deny that the picture I showed her indicated coil damage, and even had the audacity to ask me why didn't I complete the repair by replacing the coils (i.e., why didn't I pay out of my pocket $200-$300 to replace warranted parts in a 39K car)...

The problem exists, and I need to get to the bottom of it. That's why I turned to the forum.

Thanks



Buy a new or used old GoPro and tape dash while driving, just a thought. I know sometimes just throwing some money at it is worth the not having dealer aggravation. Yes, the Hyundai long warranty..........how great that is........ huh.
If you can document it on video you can always try a different dealer too. But you will need documentation, otherwise they will look at the other dealers work and blow you off too. I can kind of understand it though. It needs to fail on them to fix it. That's why multiple video verification needs to me obtained.

I would clean grounds and add another ground strap from engine to chassis. Pull out and put back in related fuse box relays and fused multiple times. Reseat ECU plug multi times. I would also use a small amount of die electric grease on coils and sparkplug cylinder head tubes he coil/plug paint is worn. Both surfaces. Very lighly since the grease will melt and drip down.
 
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