P0300 code

[BarryC]

Good day all,
My H3 has been coding the Dreaded P0300 code! (Random cylinder misfire)
I started with the most obvious and relatively cheapest fix...new plugs.Still coded...so next I replaced the Coil packs,still codes! Only codes when It idles?! Runs perfectly fine..no misses or poor acceleration etc?!! I then cleaned the throttle body as well...still fkng codes ???!!! Doesn't appear to have any vacuum leaks either...and new fuel pump a year ago...so fuel pressure is also good! Any suggestions would be appreciated

 

[H3Hummer]

Do ya have an OBD2 reader/eraser? Did you try to clear the code?

 

[BarryC]

Absolutely did n do...also replaced the mass air flow sensor as well...been working on vehicles for over 40 years, never came across a P0300 code! Fkng pain in the ass!!!