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I've never had any problems with my Elantra before, but all of a sudden one morning my car started to vibrate violently after starting and the check engine light came on when I started to move. I stopped the car and made an appointment at the dealership. I started the car later in the day and the problem went away.

I hooked up my OBD code reader and it had P301 as a pending code. By the time I brought it to the dealer to be checked out, the pending code had cleared out. Looks like a P301 code is a cylinder 1 misfire code. Dealership couldn't find any problems after inspecting the engine.

Does anyone know why this would happen all of a sudden once and go away?
 

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Coil, fuel injector wiring may be starting to fail. Do a wiggle test of the wires going to #1 and see if you can get it to miss. Or wait until it fails again.

BTW did you check for that code again. They don't usually clear without more completed non fail starts.
 

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Coil, fuel injector wiring may be starting to fail. Do a wiggle test of the wires going to #1 and see if you can get it to miss. Or wait until it fails again.

BTW did you check for that code again. They don't usually clear without more completed non fail starts.
Pending code was completely cleared out. It was started several times since without problems
 

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Do the wiggle test. If it's a connector or associated wiring it may fail and you'll know where the problem is.
 

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I've seen this happen due to head gasket leakage letting a little coolant into the combustion chamber overnight, then it clears itself out.
So keep an eye on the coolant level.
 

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Ethanol is stupid, not saving any carbon burning because takes a gallon of fossil fuel to make a gallon of ethanol.


Also absorbs moisture that causes a spark plug to misfire, stupid laws by stupid lawmakers also far more expensive to make ethanol than the real gas, but a lot cheaper to by than ethanol free. Don't brother contacting your congressman, can't do anything that the house leader doesn't like nor understand.


Not suppose to discuss politics, but this is what it is without any technical backup. Look at the riots in Paris for the carbon tax.


Can also be a fouled spark plug, but problems like this will be constant, ethanol very erratic.
 

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My 2017 Elantra (22k miles) did the same thing out of the blue a week ago. Ended up being a coil. I actually correctly guessed it too - mine started acting up on a rainy day and that's typically when I see a bad coil show symptoms.



Repair was completely free of course, but it is a relatively easy piece to replace if you ever had to do it out of warranty. Probably a $50-$75 part or maybe even less and labor can't be more than half an hour even for a noob.
 

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I've never had any problems with my Elantra before, but all of a sudden one morning my car started to vibrate violently after starting and the check engine light came on when I started to move. I stopped the car and made an appointment at the dealership. I started the car later in the day and the problem went away.

I hooked up my OBD code reader and it had P301 as a pending code. By the time I brought it to the dealer to be checked out, the pending code had cleared out. Looks like a P301 code is a cylinder 1 misfire code. Dealership couldn't find any problems after inspecting the engine.

Does anyone know why this would happen all of a sudden once and go away?

I am currently having the same issue! Car at dealership for the 3rd time! Did your issue ever get resolved?
 

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Anyone ever get a clear resolution on this? My car is at the dealer now for this exact issue on my 2017 Elantra VE. It's extremely frustrating, because it's so intermittent. I first had the problem last Thursday on my way to work. Check Engline Light came on and car was shaking. Once I shut it off and restarted, it was fine. The following day, on my way home from work, it started up again for just a minute or two, then cleared up. Yesterday, I took it to the dealer, and they weren't able to replicate the problem or find anything wrong. So I picked my car up after work, and lo and behold on my way home, the light came on and it started shaking again. I turned right around and brought it back to the dealer, and they were able to find a pending code for a misfire in cylinder 1. They gave me a loaner and sent me on my way. However, today they have been unable to find the cause of the issue or get the misfire to trigger again. So now they want me to come in after work tomorrow to drive the car with one of their techs to see if I can somehow magically trigger it again. It's incredibly frustrating. Anyone have any thoughts?
 

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Anyone ever get a clear resolution on this? My car is at the dealer now for this exact issue on my 2017 Elantra VE. It's extremely frustrating, because it's so intermittent. I first had the problem last Thursday on my way to work. Check Engline Light came on and car was shaking. Once I shut it off and restarted, it was fine. The following day, on my way home from work, it started up again for just a minute or two, then cleared up. Yesterday, I took it to the dealer, and they weren't able to replicate the problem or find anything wrong. So I picked my car up after work, and lo and behold on my way home, the light came on and it started shaking again. I turned right around and brought it back to the dealer, and they were able to find a pending code for a misfire in cylinder 1. They gave me a loaner and sent me on my way. However, today they have been unable to find the cause of the issue or get the misfire to trigger again. So now they want me to come in after work tomorrow to drive the car with one of their techs to see if I can somehow magically trigger it again. It's incredibly frustrating. Anyone have any thoughts?
My Elantra did the same thing earlier this year. The CEL turned on and then went off when I took it to the dealer. The misfire code was still stored so the tech was able to pull it. Turned out to be a bad coil

A tech on here said he's seen a few newer Elantras come in for coils. He also said they need an active or stored code when submitting a warranty claim to Hyundai. On my paperwork, it said they performed a "coil ground test." Perhaps mention that to your dealer and see what happens.
 

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My Elantra did the same thing earlier this year. The CEL turned on and then went off when I took it to the dealer. The misfire code was still stored so the tech was able to pull it. Turned out to be a bad coil

A tech on here said he's seen a few newer Elantras come in for coils. He also said they need an active or stored code when submitting a warranty claim to Hyundai. On my paperwork, it said they performed a "coil ground test." Perhaps mention that to your dealer and see what happens.
Thanks for the suggestion. I passed it along to the dealer, and they said they've already tested the coils, but didn't find any issues there. This whole thing is getting to be extremely frustrating.
 

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I've had 2 bad coils on 2013 Accent and both tested good.. That test seems to be very inaccurate. Switch coils 1 and 2. Drive your car under hard load force it to run rough till it throws a CEL. Then check and see if your misfire code moved to Cylinder 2. If it does you have a bad coil.
 

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Thanks for the suggestion. I passed it along to the dealer, and they said they've already tested the coils, but didn't find any issues there. This whole thing is getting to be extremely frustrating.
@tc0566 has good advice. Swapping coils is very easy to do on these cars and will definitively tell you if the cyl 1 coil's bad.

I'd also go to another dealer the next time the light turns on.
 

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I got cylinder 1 misfire code not long ago. Checked oil level and it was good. We took spark plug of cylinder 1, cleaned it, put it back and cleared the code. I haven’t seen the code back on. I think the spark plugs on my car are becoming bad, I will have to replace those soon.
 

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@tc0566 has good advice. Swapping coils is very easy to do on these cars and will definitively tell you if the cyl 1 coil's bad.

I'd also go to another dealer the next time the light turns on.
They claim they tried swapping the coils, but I'm not sure how hard they drove it after. And the problem is the next closest dealer is almost an hour away.
 

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Tests will not tell you anything more than the coil is working,,sure it works fine until you actually drive it under hard load. Dealers don't get paid to diagnose without codes to prove there is a problem..swap your coils get it to show a code take it back and raise **** til they fix it.
 

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Just wanted to follow up. I had my 2nd coil go bad just a few weeks ago. I asked the mechanic if this was a documented issue but he was adamant I was the first 2017 owner to have 2 coils replaced this early. Anyway, nothing I can do about it -just monitor.

Not sure if related but shortly after the 2nd coil was replaced my battery went out (wouldn't hold over 12V). Maybe it was placebo, but my car is noticeably smoother more responsive after battery replacement. All of my previous mechanic/car experience tells me a battery shouldn't affect this but it did.

All that said, 2 coils and a battery in less than 31K miles and 2.5 years of ownership. My 2011 Elantra has 100K miles on it with all 4 original coils and the OEM battery made it over 4 years. Sad to see Hyundai quality slipping.
 

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Just wanted to follow up. I had my 2nd coil go bad just a few weeks ago. I asked the mechanic if this was a documented issue but he was adamant I was the first 2017 owner to have 2 coils replaced this early. Anyway, nothing I can do about it -just monitor.

Not sure if related but shortly after the 2nd coil was replaced my battery went out (wouldn't hold over 12V). Maybe it was placebo, but my car is noticeably smoother more responsive after battery replacement. All of my previous mechanic/car experience tells me a battery shouldn't affect this but it did.

All that said, 2 coils and a battery in less than 31K miles and 2.5 years of ownership. My 2011 Elantra has 100K miles on it with all 4 original coils and the OEM battery made it over 4 years. Sad to see Hyundai quality slipping.
Well, no coils yet on my 2017 Elantra, but the battery just died about 2 week ago. Less than 3 yrs, about 24,000 miles. Replaced under warranty. OTOH, my 2010 Elantra went 7 years and 37,000 miles on the original battery. Of course, the electrical system in 2017 puts more load on the battery than years ago.
 
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