My car has a nasty sputter at ideal at times, also lots of soot on my back bumper. ive changed everything from cap and rotor to plugs and wires and valve adjustment. and i have a CEL for EVAP purge flow. when i put the diagnosis on my car is shows the EVAP CEL and then does a check off of everything thats ok but does not check off catalyst or o2 sensor. it sounds like a dumb question but i just dont have much money to keep spending without fixing this problem. Would the sputter at idel be from the o2 sensor? searched

 

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