2012 Hyundai Elantra GLS, AT, 60k miles. No CEL or codes when scanned at AutoZone.
For the past year my car has stuttered when applying very very light throttle and the car is accelerating at the 2500-3000rpm band. OnYly happens when the acceleration is so light that the AT doesn't want to downshift but struggles to accelerate under the low torque 1.8liter engine.
One shop told me it was dirty valves from the GDI engine. But from my research my US 2012 Elantra still uses port injection. Another shop said it was probably bad gas and had me use Lucas Fuel Treatment. This didn't help the issue.
I then did some research and thought maybe it was a dirty injector so I used Gumout Complete Fuel System Cleaner. It immediately fixed the issue. However a few months later it is happening again but a lot less frequently. Should I just run another bottle of Gumout or do I need to start looking deeper? I thought about buying a scan tool for the live data but afraid a $100 unit won't show me enough data.
Given the age of the vehicle, mileage, and information you provided, I would suggest pulling the spark plugs and the injectors to check and make sure nothing is dirty or fouled. You may have a dirty/partially clogged injector that is not spraying enough fuel causing the misfire as that would explain why the cleaner temporarily helped out. The good news is that injectors can be placed in a fresh gasoline bath to soak and removed clogs in some cases saving you the cost of replacing an injector. Alternatively, there are still shops out there that have injector service machines that cycle and test the injector to clean and verify if any is damaged and need replaced. Check out this YouTube video for how to remove the injectors yourself:
https://www.youtube.com/watch?v=iOdmy8Fm1gs&feature=emb_title&ab_channel=AutoRepairGuys
