Originally Posted by
Padgett
What are the other codes ? P0300 is a generic code but P030x (x=1:6) tell which cyl is an issue.
Most usual cause is a high voltage (coil, wires, plug) breakdown and they usually start small then get worse.
That last non-zero digit says which cyl it is (and a P030x just means the computer detected a rpm slowdown when that cyl was supposed to fire so could also be mechanical) but need to know what those other codes were.
The X code changes after each code clear... It's always a random mix of 2 or 3 cyl's... Which is why I was starting to think it's not coils.