I have an 03 kia rio and am having power issues. The check engine light is on and the car simply fails to go when the gas is depressed. It acts like its starving for fuel and sounds like its only running on 3 cylenders. I have replaced the mass air flow sensor,plugs and wires.Please help as this issue has almost got my wife hit while pulling out to make a turn .It has died a few times. It has days it will do this and days it wont.Thank you for your help.

I have the same issue with mine and found that if you gap the plugs to .026 -.028 instead of the factory settings of about .042 that the issue is 95% gone. I had changed the coil, plugs and wires before I found this remedy. The issues resurfaces now and then but not nearly as bad. Reset the ecm by pulling the 10 amp fuse in the under hood panel and it'll run better also. Stick with regular plugs, not platinum or others.

Make sure you replace the fuel filter every 35000 miles.
Also, when it sounds like its running on 3 cylinders,check to see if spark is coming out of the coil.
With the engine off take the spark plug wires loose and just set them on the plug lightly so they can be removed easy.
You will need plastic plyers or something insulated to remove and replace the wires.
Start the engine and one at a time remove the wire from the plug and see if it makes a difference or not.Then replace it and go to the next wire.
If it runs worse put that wire back on tight because its fine.
If it runs the same with the wire off then that is a problem cylinder.
Your should hear a spark snaping with the wire pulled slightly away from the plug.
If its not sparking (snaping sound) then that coil is bad and needs new one.
I hope this helps you.

What trouble codes are represented, since the check engine light is on? Let's start there.