Honda fit sputtering

My 2007 honda fit had some sputtering problems while on idle. I knew car
suffers from this so i replaced all 4 coils and spark plugs. That seemed to be
its problem throughout the past years but now the problem persists even
though coils, spark plugs were replaced. CEL was on so I scanned it for codes
and it threw a P1100 or  something indicating  it was the O2 sensor so I
replaced it. I also replaced the fuel pump filter and check engine light turned
off but the engine is still giving me that sputtering failure. No CEL like I said,
And dunno what else could it be. Any suggestions? Car has 184k miles on it
and I am the sole owner. Thanks