05 mazda 3 2.3L has p0300 code runs fine tho any ideas?

 

P0300 is Random misfire.

Have anything been touched, moved or cleaned under the bonnet lately?

 

Light was on when I got the car I checked the plugs they were clean put new ones in anyway drove 3000 miles and checked again still looked new did a compression check all good just noticed the light will flash a couple of seconds when going down hill or if I accelerate and than let go of the throttle

 

If you take it to Mazda they can look up the history on their diagnostic computer & view the misfire history of each cylinder, even without any fault codes.