I have a 2007 Saturn ION, been wonderful so far, I have a little over 90,000 mi on it, now my "check engine" light appears then disappears, I'm getting the p0300 error, something about it misfiring, It idles poorly and when the "check engine" light is lit up, it tends to "kick" as I accelerate, but seems to run well when the "engine" light is NOT lit up, any "idears"

I've had the same problem before. Autozone had a code reader and said that it was/had misfired on cylinder #3, which will trigger the check engine light. Start with the cheapest and easiest fix first, install new spark plugs. If that works, great!! If not, install new plug wires. See where I'm going? Keep going with the simple fixes and hopefully this will solve your problem. Keep in mind, the L61 engine that's in your car is one of GM's best designs.

Misfire can be elect or fuel related---possibilities are fuel filter/fuel pump--coil going bad --plug wire going or damaged --plug going-cap cracked aged --check plugs if need replacing give car tune up and change fuel filter w/90,000 its due