Have a 2003 S2000 with K&N cold induction. Car is running rough sometimes. The rough running comes and goes away. Very confused what is wrong with it. It runs very good then all of a sudden it's start to buck. The engine light is on for a P0411. This shouldn't cause engine misfire. Confused!

 

Do some searching on the code.

P0411 Secondary Air Injection System Incorrect Flow Detected

You could have a vacuum leak which can cause the engine to run rough.

Also, check out this thread. https://www.s2ki.com/s2000/topic/350254-cel-p0411/

 

I have this same code lately.It is a vac leak more times that not.It does NOT affect the perf of my 03 at all.

\rlr
Carolina