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Discussion Starter · #1 · (Edited)
Hey guys, I have a 2017 Elantra Sport with 71,XXX miles. About 5 weeks ago I ran into a store to grab coffee and came back out to start my car and it refused to fully start (see video link). It sounds like it's trying to but just refuses. Eventually after cranking it a few times it'll start up just fine and be good for anywhere from a few days to about two weeks before doing it again. I've already replaced my spark plugs and gotten the battery, alternator, and starter tested (stated they were 100% functional with no obvious issues), still pulling about 14 volts with the battery too.


Here's my short list of things I'm considering are wrong.
  • Bad grounds.
  • Bad ignition coils (although looked fine when I did the spark plugs)
  • Bad fuel filter See below
  • Car just hates me.
  • Maybe a fuse or relay?
  • Crankshaft position sensor.
My current mod list.
  • SXTH Cold Air Intake.
  • SXTH AV6 BOV.
  • Braided PCV lines (came with intake)
  • Muffler delete.
  • BC Racing Coilovers.
Anyone have the slightest idea what it could be before I just drive it into oncoming traffic? Thanks a bunch!

UPDATE: I tested the fuel pump today and it's working flawlessly so I can rule that out. After spending about an hour talking to a friend who is a Hyundai Master Tech he told me to try changing the crankshaft position sensor, luckily it's only $27 and will be here this weekend so I will let you guys know. I am also running a fuel system cleaner as well just to ensure that the lines are free of junk and dirt.

UPDATE 2: Put a new crankshaft position sensor in on 7/4/22 and it seems to have fixed the issue, will update if anything else happens.
 

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2018 Hyundai Elantra Sport DCT w/TECH
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341 Posts
Do you have any aftermarket remote start or immobiliser?
Ideally it would be best to hook up the GDS and check what signals are missing, if any.
Is the engine running perfectly fine once started?
 

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Discussion Starter · #3 ·
Do you have any aftermarket remote start or immobiliser?
Ideally it would be best to hook up the GDS and check what signals are missing, if any.
Is the engine running perfectly fine once started?
No aftermarket remote start or immobilizer. Once started engine runs totally fine, no issues at all. I did replace the crankshaft position sensor over the weekend and it seems to have stopped the issue (knock on wood) so we'll see.
 

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Hyundai elantra SR 2017
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Mine started doing the same recently, did most of what you have done apart from the crankshaft sensor, sounds like I'll need to do the same. Thanks for the thread bro hope you still haven't had any issues 🙏
 

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Discussion Starter · #5 ·
Mine started doing the same recently, did most of what you have done apart from the crankshaft sensor, sounds like I'll need to do the same. Thanks for the thread bro hope you still haven't had any issues 🙏
So far I've been issue free (still knocking on wood lol). The sensor was kind of a PITA to do. It's only one 10mm socket, but the space is very tight and the clip that holds the wire in is very hard to get out, I had to really pull on it to pop it loose. If you need any guidance in changing the part lmk and I can give you a full walkthrough. The part I bought was only $27 on Amazon and took about an hour to install.
 

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Hyundai elantra SR 2017
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So far I've been issue free (still knocking on wood lol). The sensor was kind of a PITA to do. It's only one 10mm socket, but the space is very tight and the clip that holds the wire in is very hard to get out, I had to really pull on it to pop it loose. If you need any guidance in changing the part lmk and I can give you a full walkthrough. The part I bought was only $27 on Amazon and took about an hour to install.
I changed the sensor 4days ago and haven't had any problems since 👍
 
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