Ok here's the deal. 05 aveo 150k miles I just got it. Thirty seconds of driving, check engine light starts flashing meaning misfire. Car runs fine with plenty of power. Plug in scanner sure as **** p0300 and is only code. Look at misfire data, isnt ticking any misfires even though ses light is flashing... kinda weird if you ask me usually flashing means hard misfire... anyway so I drive it and once in a blue moon it ticks history misfires on 2 and 3. Ok sure do a tune up with new coil... problem is still there. Also when I first got car it wouldn't start cause of corrosion on crank sensor. I cleaned it and also did crank variation relearn attempting to fix issue so it starts now just misfires... anyway I'm thinking I might have a valve issue but would just like some input before I drop several hundred on parts. If that is the issue would just valves fix it or would I need a head? Will a leak down show this very intermittent misfire? Or maybe my crank sensor is stupid causing it to tick false misfires? I'm out of ideas and ways to test **** I appreciate your time thanks.