Engine misfire and jerking

You'll first want to get the car scanned or buy a code scanner for yourself like this. That said, I know from experience with these older Kias that predate the faulty Georgia factory engines CAN be better then the newer engines (but are prone to oil consumption). In the meantime, see if you can siphon some gas from the tank and make sure you do not have bad gas using a kit like this kit.

Look for a misfire code, and start there; that's what it was for me when I had to look at a Forte from this period with the 2L i4. The component that caused problems in the one I looked at was the ignition coil, but I would start by replacing all four spark plugs if you see misfire codes, as it's a cheaper repair than the ignition coils. Make sure you clear the code so it stays out of the OBD2 code history. Once you swap the spark plugs with the same issue, move one of the ignition coils to another cylinder to see if the code moves; if it does, you know it's the ignition coil.

READ: Some Kias do not give you proper codes and refuse to move the original DTC, which can trip you if you are unaware. Ultimately, using an all-system code scanner will tell you if it helps, as you can do things like live data and get OE codes, but they're pricey; my Xtool is just about in the $300 ballpark. Swapping the coil will likely be cheaper than a $300 scan tool if you do not see the code move and know you have one of these "difficult" Kias. It's a quirk from the Hyundai ECU.

If changing the isolated ignition coil does not help, you may want to change the remaining coils, as the others may be on their way out, and check to make sure the injectors are good. If the injectors are fine (or you decide to try before condemning the car) and EVERYTHING ELSE (including the coils) has been checked over, you may have a more serious issue, like a bad engine. That said, before condemning the engine/car (assuming you have done everything else, mainly gas check/spark plugs/fuel injectors/coils), do two things:

• Pressure test the cylinders. Find the SM and see the tolerances Hyundai expects with your engine; usually with Hyundai/Kia, 100Kpm variation is "acceptable" below the minimum.
  • Make sure you pull the fuel pump relay beforehand. It will create codes so you probably want to buy a scan tool before doing this to clear them out.

This is what the page should look like (Note this is an EXAMPLE; find the SM for your Rio and locate the info specific to yours):

That said, here's the specific data for yours.

• Get a borescope camera like this and check for issues like scoring in the piston rings, and severe oil consumption.