2013 Hyundai i30 Gasoline: Check Engine Light, Rough Idle, Black Smoke, and Excessive Fuel Consumption Issues

Hey there, I've had a very similar problem with my 2011 Hyundai Elantra, so understand your frustration. Although I've only got some experience tinkering around with cars, here's what I did to fix the issue. Turned out that the wiring harness/plug was defective, which might be the issue with your Hyundai i30 as well. Managed to diagnose the problem at a local workshop. These guys were real pros, kept me informed throughout and sorted it out without a hitch. Paid around 95€ to have this fixed - pretty reasonable, considering I was initially fearing a costly fuel pump issue. Your symptoms sound oddly similar, so might be worth getting the wiring checked out. By the way, could you share some extra info like mileage, any previous repairs, etc.? It may help me (and others on the forum) advise you a bit better. Hope this helps!

Hey, really appreciate the help. My i30's at around 51207 KM now, but never had any big repairs, except for the usual maintenance stuff. The last service was recently, with them only changing engine oil and rotating the tires. Didn't notice any issues then, so this stuff's all pretty sudden. Definitely gonna get a pro to look at the wiring harness, since I don't have the equipment to test it myself. Will report back once I've got this mystery solved. Thanks again for the insight, truly helps!

No worries! Based on the mileage and maintenance history you've provided, it seems like your Hyundai i30 is relatively well taken care of. The sudden issues are indeed puzzling, but cars can act up unexpectedly sometimes. Since your last service was pretty recent though, I wonder if something could’ve been accidentally dislodged or a component weakened during one of those processes. It’s a long shot though, and not necessarily something you should worry about too much. In any case, getting a professional look at it would rule out any uncertainties. You're on the right path focussing on the wiring harness. If it's a similar problem like mine, it won't be too costly to get it fixed. Don't forget to keep us posted on how it goes at the workshop. Fingers crossed it’s something simple like this and not a fuel pump issue. Good luck!

Hey there, thanks for the encouragement and tips. Could be possible something got messed during the last service, wouldn't really know though. Been a crazy day of taking guesses here! Agreed, getting it checked professionally is the way to go now. As soon as I got any news on the situation, I'll make sure to update here. Hoping it turns out to be something insignificant, fingers crossed. Till then, take care and thanks again!