P0304 intermittent misfire only in first... on accel


Hello and thanks … 2005 Rio with 130 000 - 5 speed … burning a bit of oil but otherwise runs ok.

Car runs and drives without problems, but once in a while, several times a week, it will miss fire on take off. Starting out in first, it will hesitate, lose power; I feather the gas, the RPM’s come back and car runs normal . However, If I go WOT , the car will set a soft 304, it will continue to run rough, until I restart the car, the MIL is off and car is ok.

I have done a tune up, plugs wires, coil, and replaced wires connecting to the coil. Any thought would be helpful thank you

Check valve clearance. Do a compression test.

Replace the knock sensor. I also have a Kia Rio and had the same problem. Replaced the sensor, cleared the code a walaa it runs great again. As for the smoking when you first start it, mine too, it’s the valve guides. I go through about a quart of oil in my 3500 miles between oil changes.