2009 Fit Sport @ 249K kms had a slight fuel smell on startup for a few weeks and finally gave a P0303 third cylinder misfire code.
The code would return when the car would cool for about 30 minutes and then started and just idled.
Did not really notice rough running or reduced fuel mileage.

Upon investigation today found both the #2 and 3 plugs only finger tight and both plug boots stained by blow-by .

Changed all four plugs and cleaned the boots and all appears to be back to normal. Will update if needed.

Thought someone may be able to use this information.

 

That is extremely common in GD and GE Fits.

Keep an eye on them or they could eject and take the spark plug threads with them.