I do not think she has smart cruise controlDoes she happen to have the smart cruise control set and then happen to be lightly pressing the accelerator? That will happen sometimes with mine where I have the smart cruise set and then sometimes I'll press the gas to get around someone or break up with a pacing vehicle and my car will surge like you've described until I either let off the gas or bump the set cruise speed up a few miles.
@jessepaws21 Kind of like that. What are the things they told to do?I have this issue where at a constant speed the car will occasionally jerk forward and then backward, almost as if you can feel the car changing gears. Weird because before 36000 miles it never happened. Talked to hyundai and they said they didn't feel anything while test driving it, and told me a number of things it could be and what fix they had. Is it something like that?
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Well, first thing they did was reset the transmission control module via software update, then decided to drive with their technician. The scanned for codes and CEL and nada. They saw I was due for my 37k maintenance and recommended that air filter and fuel cleaner be used and sent me on my way. They let me know that they've seen this a lot with this generation of sonata, and that between me and the service manager, they think the transmissions were very hit and miss. He said if it continues to happen or gets worse, I'd have to come back to have the transmission switched out.
I dont know if the 2015 has the mode selection "Eco-Sport Normal" but it is a LF model so i suspect it does. Have he try changing to "eco" and see if it helps. Changing the mode to "Eco" changes the shift points and decreases the accelerator responsiveness so if it is caused by her driving habits and not a mechanical problem this may help.
Other things to try are a fuel system cleaner if it is injectors or plugs, it may help or an intake cleaning as in other threads this engine can build up carbon on the intake valves and may need an intake cleaning, if you dont want to DIY it with a cleaner like CRC GDI Intake Cleaner try to find a shop that offers BG Products and have them do the GDI system cleaning. BG offers a complete service that does a good job.
Has it ever been on connected to a OBD to check for codes? How many miles on it, may just need service- plugs, air cleaner etc.