This is regarding a 98 Prelude. Many H22s experience a hesitation around 3k rpm due to carbon build-up in the egr port in the intake manifold. So, I ran half a can of seafoam through. The hesitation is gone now, but I'm getting misfire codes. Usually it's just on cyl1, sometimes cyl 1 and 3. Plugs have changed and valve adjustment has been done. Still having the problem. Any ideas?

Is it possible that the O2 sensor(s) got messed up and/or cat from all the carbon? Any other ideas?

Parts that are less than 10k miles old: Cap/rotor, plugs, wires, fuel filter, etc.

 

So i am assuming you have cleared these codes and they keep returning, correct?

 

Yes.

 

Does the car stumble an have rough idle? or are the misfire codes just poping on and the vehicle running fine?

If ur car is running rough u might have a crack in ur cylinder head or valves

 

change the spark plugs.