2014 Veloster Turbo Automatic
TRDTroy is right, flashing CEL usually means misfire. If you're getting a misfire on 3, then switch the coil pack from cyl 3 to cyl 2, and vice versa. If the misfire moves, then it's likely the coilpack. I had an identical situation last week right before a track day. Brand new (<5000 miles) coil from O'Reily's decided to shit the bed right after I swapped the fuel line. Flashing CEL and everything. Swapped the coil from 3 to 2, then the misfire moved with it. Swapped it out with some OEM coils and the car runs great.That makes sense. I don't know, I'm panicking. My car has been amazing. Just put a ton of money down for a home and then the car starts acting up. That's life, right? I think you are on the right path, It feel like misfiring. I think the code was a misfire on 3. And it's only when I depress the accelerator past halfway. Idles fine. Slow acceleration is fine. It's when its under demand. I know they rotated the coils and plugs to see if they would throw a code, and it didn't. It ran amazing after the injectors were changed. One of my plugs had a crack in the ceramic one time, so maybe it happened again? I'll start there.
Thanks for your help and suggestions, BTW.
specifically regarding what the dealer did: My coilpack only acted up when then engine was at operating temperature and driving. It idled and revved up fine, but would only throw the CEL after driving for a bit. Get the car nice and warm, then see if you can replicate exactly what it takes to get the CEL to pop up. My method was to drive it normally for about 10 minutes, then do some hard 2nd and 3rd gear pulls. By the second pull, it would always throw the CEL and sputter like you described earlier.